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Erase minutes and seconds from character dates in R



The Next CEO of Stack OverflowSelect every other element from a vectorIn R, split a character vector by a specific character; save 3rd piece in new vectorHow to Correctly Use Lists in R?Identifying unique terms from list of character vectorsConvert data.frame columns from factors to charactersRemove quotes from a character vector in RReplace specific characters within stringsdata.table vs dplyr: can one do something well the other can't or does poorly?In R, how do I extract minutes and seconds from charactersCalculate character string “days, hours, minutes, seconds” to numeric total daysFrom sessions to minute by minute summaryConvert character vector to a new vector of substrings










2















I have this timestamp vector:



c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
"01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
"01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
"01/09/2019 10:52:20")


I'd like to strip off the minutes and seconds from the character vector so that I just have 01/09/2019 9 and 01/09/2019 10



What is the most efficient method to do so?










share|improve this question






















  • Interesting accepted answer, what is your definition of efficient?

    – Hector Haffenden
    Mar 22 at 12:53











  • I'm pretty biased towards tidyverse packages :)

    – JasonBaik
    Mar 22 at 14:40











  • ah I see, I don’t blame you :) next time you should probably put it in the question...

    – Hector Haffenden
    Mar 24 at 19:07















2















I have this timestamp vector:



c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
"01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
"01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
"01/09/2019 10:52:20")


I'd like to strip off the minutes and seconds from the character vector so that I just have 01/09/2019 9 and 01/09/2019 10



What is the most efficient method to do so?










share|improve this question






















  • Interesting accepted answer, what is your definition of efficient?

    – Hector Haffenden
    Mar 22 at 12:53











  • I'm pretty biased towards tidyverse packages :)

    – JasonBaik
    Mar 22 at 14:40











  • ah I see, I don’t blame you :) next time you should probably put it in the question...

    – Hector Haffenden
    Mar 24 at 19:07













2












2








2


0






I have this timestamp vector:



c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
"01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
"01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
"01/09/2019 10:52:20")


I'd like to strip off the minutes and seconds from the character vector so that I just have 01/09/2019 9 and 01/09/2019 10



What is the most efficient method to do so?










share|improve this question














I have this timestamp vector:



c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
"01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
"01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
"01/09/2019 10:52:20")


I'd like to strip off the minutes and seconds from the character vector so that I just have 01/09/2019 9 and 01/09/2019 10



What is the most efficient method to do so?







r






share|improve this question













share|improve this question











share|improve this question




share|improve this question










asked Mar 21 at 1:02









JasonBaikJasonBaik

406114




406114












  • Interesting accepted answer, what is your definition of efficient?

    – Hector Haffenden
    Mar 22 at 12:53











  • I'm pretty biased towards tidyverse packages :)

    – JasonBaik
    Mar 22 at 14:40











  • ah I see, I don’t blame you :) next time you should probably put it in the question...

    – Hector Haffenden
    Mar 24 at 19:07

















  • Interesting accepted answer, what is your definition of efficient?

    – Hector Haffenden
    Mar 22 at 12:53











  • I'm pretty biased towards tidyverse packages :)

    – JasonBaik
    Mar 22 at 14:40











  • ah I see, I don’t blame you :) next time you should probably put it in the question...

    – Hector Haffenden
    Mar 24 at 19:07
















Interesting accepted answer, what is your definition of efficient?

– Hector Haffenden
Mar 22 at 12:53





Interesting accepted answer, what is your definition of efficient?

– Hector Haffenden
Mar 22 at 12:53













I'm pretty biased towards tidyverse packages :)

– JasonBaik
Mar 22 at 14:40





I'm pretty biased towards tidyverse packages :)

– JasonBaik
Mar 22 at 14:40













ah I see, I don’t blame you :) next time you should probably put it in the question...

– Hector Haffenden
Mar 24 at 19:07





ah I see, I don’t blame you :) next time you should probably put it in the question...

– Hector Haffenden
Mar 24 at 19:07












6 Answers
6






active

oldest

votes


















1














You could also use str_extract from stringr:



date_strings <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
"01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
"01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
"01/09/2019 10:52:20")

str_extract(date_strings, ".+(?=:.+:)")

[1] "01/09/2019 9" "01/09/2019 9" "01/09/2019 9" "01/09/2019 10"
[5] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"
[9] "01/09/2019 10" "01/09/2019 10"





share|improve this answer






























    3














    Here's one.



    datevec <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
    "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
    "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
    "01/09/2019 10:52:20")

    format(as.POSIXct(datevec, format = "%d/%m/%Y %H:%M:%OS"), "%d/%m/%Y %H")

    # Result
    [1] "01/09/2019 09" "01/09/2019 09" "01/09/2019 09" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"
    [7] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"





    share|improve this answer
































      2














      What is your desired output class? How about this one:



      v <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
      "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
      "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
      "01/09/2019 10:52:20")


      strptime(v, "%m/%d/%Y %H")





      share|improve this answer
































        2














        This seems nice,



        unlist(strsplit(mystring, split = ":", fixed=TRUE))[c(TRUE, FALSE,FALSE)]


        (Made with help from here)



        Alternative could be,



        sapply(strsplit(mystring, split=':', fixed=TRUE), `[`, 1)


        Using some benchmarks and recent comments by Ronak, that fixed=TRUE makes the methods a lot faster, we see that method four (the above method) is fastest,



        mystring <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
        "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
        "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
        "01/09/2019 10:52:20")

        microbenchmark(one = sapply(strsplit(mystring, split=':', fixed=TRUE), `[`, 1),
        two = unlist(lapply(mystring,function(x) strsplit(x,":", fixed=TRUE)[[1]][1])),
        three = strptime(mystring, "%m/%d/%Y %H"),
        four = unlist(strsplit(mystring, split = ":", fixed=TRUE))[c(TRUE, FALSE,FALSE)],
        five = format(as.POSIXct(mystring, format = "%d/%m/%Y %H:%M:%OS"), "%d/%m/%Y %H"),
        six = gsub("(.*?):.*", "\1", mystring),
        seven = str_extract(mystring, ".+(?=:.+:)"),
        times = 100000)



        Unit: microseconds
        expr min lq mean median uq max neval
        one 42.792 49.471 85.63742 52.572 57.1310 669280.96 1e+05
        two 64.637 70.618 114.16364 73.252 77.6840 582466.94 1e+05
        three 129.456 134.771 156.82308 136.188 139.2030 339715.94 1e+05
        four 12.860 15.641 22.75699 17.254 18.5440 305703.52 1e+05
        five 482.888 505.647 633.15388 512.880 552.1155 551274.28 1e+05
        six 37.889 43.121 52.79030 45.567 49.1880 32954.59 1e+05
        seven 53.432 59.051 88.05015 62.326 69.9320 1180361.17 1e+05





        share|improve this answer

























        • yep. I think fixed = TRUE makes it a lot faster.

          – Ronak Shah
          Mar 21 at 1:40






        • 1





          Very interesting, actually 4, with fixed=TRUE is fastest, changed the benchmark to show this.

          – Hector Haffenden
          Mar 21 at 1:43



















        0














        Another one:



        dates <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
        "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
        "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
        "01/09/2019 10:52:20")
        unlist(lapply(dates,function(x) strsplit(x,":")[[1]][1]))


        gives



         [1] "01/09/2019 9" "01/09/2019 9" "01/09/2019 9" "01/09/2019 10" "01/09/2019 10"
        [6] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"





        share|improve this answer






























          0














          Here is another one using gsub



          Capture the pattern by () and \1 to refer to the captured group, need ?to make regex lazy as there are multiple :.



          gsub("(.*?):.*", "\1", dates)





          share|improve this answer























          • Added to my benchmarking answer, hope thats okay.

            – Hector Haffenden
            Mar 21 at 2:17












          • All good, its great to see those benchmarks.

            – MKa
            Mar 21 at 2:55











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          6 Answers
          6






          active

          oldest

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          6 Answers
          6






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          1














          You could also use str_extract from stringr:



          date_strings <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
          "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
          "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
          "01/09/2019 10:52:20")

          str_extract(date_strings, ".+(?=:.+:)")

          [1] "01/09/2019 9" "01/09/2019 9" "01/09/2019 9" "01/09/2019 10"
          [5] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"
          [9] "01/09/2019 10" "01/09/2019 10"





          share|improve this answer



























            1














            You could also use str_extract from stringr:



            date_strings <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
            "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
            "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
            "01/09/2019 10:52:20")

            str_extract(date_strings, ".+(?=:.+:)")

            [1] "01/09/2019 9" "01/09/2019 9" "01/09/2019 9" "01/09/2019 10"
            [5] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"
            [9] "01/09/2019 10" "01/09/2019 10"





            share|improve this answer

























              1












              1








              1







              You could also use str_extract from stringr:



              date_strings <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
              "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
              "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
              "01/09/2019 10:52:20")

              str_extract(date_strings, ".+(?=:.+:)")

              [1] "01/09/2019 9" "01/09/2019 9" "01/09/2019 9" "01/09/2019 10"
              [5] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"
              [9] "01/09/2019 10" "01/09/2019 10"





              share|improve this answer













              You could also use str_extract from stringr:



              date_strings <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
              "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
              "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
              "01/09/2019 10:52:20")

              str_extract(date_strings, ".+(?=:.+:)")

              [1] "01/09/2019 9" "01/09/2019 9" "01/09/2019 9" "01/09/2019 10"
              [5] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"
              [9] "01/09/2019 10" "01/09/2019 10"






              share|improve this answer












              share|improve this answer



              share|improve this answer










              answered Mar 21 at 17:06









              Ben GBen G

              911321




              911321























                  3














                  Here's one.



                  datevec <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                  "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                  "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                  "01/09/2019 10:52:20")

                  format(as.POSIXct(datevec, format = "%d/%m/%Y %H:%M:%OS"), "%d/%m/%Y %H")

                  # Result
                  [1] "01/09/2019 09" "01/09/2019 09" "01/09/2019 09" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"
                  [7] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"





                  share|improve this answer





























                    3














                    Here's one.



                    datevec <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                    "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                    "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                    "01/09/2019 10:52:20")

                    format(as.POSIXct(datevec, format = "%d/%m/%Y %H:%M:%OS"), "%d/%m/%Y %H")

                    # Result
                    [1] "01/09/2019 09" "01/09/2019 09" "01/09/2019 09" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"
                    [7] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"





                    share|improve this answer



























                      3












                      3








                      3







                      Here's one.



                      datevec <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                      "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                      "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                      "01/09/2019 10:52:20")

                      format(as.POSIXct(datevec, format = "%d/%m/%Y %H:%M:%OS"), "%d/%m/%Y %H")

                      # Result
                      [1] "01/09/2019 09" "01/09/2019 09" "01/09/2019 09" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"
                      [7] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"





                      share|improve this answer















                      Here's one.



                      datevec <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                      "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                      "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                      "01/09/2019 10:52:20")

                      format(as.POSIXct(datevec, format = "%d/%m/%Y %H:%M:%OS"), "%d/%m/%Y %H")

                      # Result
                      [1] "01/09/2019 09" "01/09/2019 09" "01/09/2019 09" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"
                      [7] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"






                      share|improve this answer














                      share|improve this answer



                      share|improve this answer








                      edited Mar 21 at 1:32

























                      answered Mar 21 at 1:09









                      hmhensenhmhensen

                      7621718




                      7621718





















                          2














                          What is your desired output class? How about this one:



                          v <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                          "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                          "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                          "01/09/2019 10:52:20")


                          strptime(v, "%m/%d/%Y %H")





                          share|improve this answer





























                            2














                            What is your desired output class? How about this one:



                            v <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                            "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                            "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                            "01/09/2019 10:52:20")


                            strptime(v, "%m/%d/%Y %H")





                            share|improve this answer



























                              2












                              2








                              2







                              What is your desired output class? How about this one:



                              v <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                              "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                              "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                              "01/09/2019 10:52:20")


                              strptime(v, "%m/%d/%Y %H")





                              share|improve this answer















                              What is your desired output class? How about this one:



                              v <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                              "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                              "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                              "01/09/2019 10:52:20")


                              strptime(v, "%m/%d/%Y %H")






                              share|improve this answer














                              share|improve this answer



                              share|improve this answer








                              edited Mar 21 at 1:30

























                              answered Mar 21 at 1:13









                              Ozan147Ozan147

                              2,0521519




                              2,0521519





















                                  2














                                  This seems nice,



                                  unlist(strsplit(mystring, split = ":", fixed=TRUE))[c(TRUE, FALSE,FALSE)]


                                  (Made with help from here)



                                  Alternative could be,



                                  sapply(strsplit(mystring, split=':', fixed=TRUE), `[`, 1)


                                  Using some benchmarks and recent comments by Ronak, that fixed=TRUE makes the methods a lot faster, we see that method four (the above method) is fastest,



                                  mystring <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                                  "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                                  "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                                  "01/09/2019 10:52:20")

                                  microbenchmark(one = sapply(strsplit(mystring, split=':', fixed=TRUE), `[`, 1),
                                  two = unlist(lapply(mystring,function(x) strsplit(x,":", fixed=TRUE)[[1]][1])),
                                  three = strptime(mystring, "%m/%d/%Y %H"),
                                  four = unlist(strsplit(mystring, split = ":", fixed=TRUE))[c(TRUE, FALSE,FALSE)],
                                  five = format(as.POSIXct(mystring, format = "%d/%m/%Y %H:%M:%OS"), "%d/%m/%Y %H"),
                                  six = gsub("(.*?):.*", "\1", mystring),
                                  seven = str_extract(mystring, ".+(?=:.+:)"),
                                  times = 100000)



                                  Unit: microseconds
                                  expr min lq mean median uq max neval
                                  one 42.792 49.471 85.63742 52.572 57.1310 669280.96 1e+05
                                  two 64.637 70.618 114.16364 73.252 77.6840 582466.94 1e+05
                                  three 129.456 134.771 156.82308 136.188 139.2030 339715.94 1e+05
                                  four 12.860 15.641 22.75699 17.254 18.5440 305703.52 1e+05
                                  five 482.888 505.647 633.15388 512.880 552.1155 551274.28 1e+05
                                  six 37.889 43.121 52.79030 45.567 49.1880 32954.59 1e+05
                                  seven 53.432 59.051 88.05015 62.326 69.9320 1180361.17 1e+05





                                  share|improve this answer

























                                  • yep. I think fixed = TRUE makes it a lot faster.

                                    – Ronak Shah
                                    Mar 21 at 1:40






                                  • 1





                                    Very interesting, actually 4, with fixed=TRUE is fastest, changed the benchmark to show this.

                                    – Hector Haffenden
                                    Mar 21 at 1:43
















                                  2














                                  This seems nice,



                                  unlist(strsplit(mystring, split = ":", fixed=TRUE))[c(TRUE, FALSE,FALSE)]


                                  (Made with help from here)



                                  Alternative could be,



                                  sapply(strsplit(mystring, split=':', fixed=TRUE), `[`, 1)


                                  Using some benchmarks and recent comments by Ronak, that fixed=TRUE makes the methods a lot faster, we see that method four (the above method) is fastest,



                                  mystring <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                                  "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                                  "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                                  "01/09/2019 10:52:20")

                                  microbenchmark(one = sapply(strsplit(mystring, split=':', fixed=TRUE), `[`, 1),
                                  two = unlist(lapply(mystring,function(x) strsplit(x,":", fixed=TRUE)[[1]][1])),
                                  three = strptime(mystring, "%m/%d/%Y %H"),
                                  four = unlist(strsplit(mystring, split = ":", fixed=TRUE))[c(TRUE, FALSE,FALSE)],
                                  five = format(as.POSIXct(mystring, format = "%d/%m/%Y %H:%M:%OS"), "%d/%m/%Y %H"),
                                  six = gsub("(.*?):.*", "\1", mystring),
                                  seven = str_extract(mystring, ".+(?=:.+:)"),
                                  times = 100000)



                                  Unit: microseconds
                                  expr min lq mean median uq max neval
                                  one 42.792 49.471 85.63742 52.572 57.1310 669280.96 1e+05
                                  two 64.637 70.618 114.16364 73.252 77.6840 582466.94 1e+05
                                  three 129.456 134.771 156.82308 136.188 139.2030 339715.94 1e+05
                                  four 12.860 15.641 22.75699 17.254 18.5440 305703.52 1e+05
                                  five 482.888 505.647 633.15388 512.880 552.1155 551274.28 1e+05
                                  six 37.889 43.121 52.79030 45.567 49.1880 32954.59 1e+05
                                  seven 53.432 59.051 88.05015 62.326 69.9320 1180361.17 1e+05





                                  share|improve this answer

























                                  • yep. I think fixed = TRUE makes it a lot faster.

                                    – Ronak Shah
                                    Mar 21 at 1:40






                                  • 1





                                    Very interesting, actually 4, with fixed=TRUE is fastest, changed the benchmark to show this.

                                    – Hector Haffenden
                                    Mar 21 at 1:43














                                  2












                                  2








                                  2







                                  This seems nice,



                                  unlist(strsplit(mystring, split = ":", fixed=TRUE))[c(TRUE, FALSE,FALSE)]


                                  (Made with help from here)



                                  Alternative could be,



                                  sapply(strsplit(mystring, split=':', fixed=TRUE), `[`, 1)


                                  Using some benchmarks and recent comments by Ronak, that fixed=TRUE makes the methods a lot faster, we see that method four (the above method) is fastest,



                                  mystring <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                                  "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                                  "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                                  "01/09/2019 10:52:20")

                                  microbenchmark(one = sapply(strsplit(mystring, split=':', fixed=TRUE), `[`, 1),
                                  two = unlist(lapply(mystring,function(x) strsplit(x,":", fixed=TRUE)[[1]][1])),
                                  three = strptime(mystring, "%m/%d/%Y %H"),
                                  four = unlist(strsplit(mystring, split = ":", fixed=TRUE))[c(TRUE, FALSE,FALSE)],
                                  five = format(as.POSIXct(mystring, format = "%d/%m/%Y %H:%M:%OS"), "%d/%m/%Y %H"),
                                  six = gsub("(.*?):.*", "\1", mystring),
                                  seven = str_extract(mystring, ".+(?=:.+:)"),
                                  times = 100000)



                                  Unit: microseconds
                                  expr min lq mean median uq max neval
                                  one 42.792 49.471 85.63742 52.572 57.1310 669280.96 1e+05
                                  two 64.637 70.618 114.16364 73.252 77.6840 582466.94 1e+05
                                  three 129.456 134.771 156.82308 136.188 139.2030 339715.94 1e+05
                                  four 12.860 15.641 22.75699 17.254 18.5440 305703.52 1e+05
                                  five 482.888 505.647 633.15388 512.880 552.1155 551274.28 1e+05
                                  six 37.889 43.121 52.79030 45.567 49.1880 32954.59 1e+05
                                  seven 53.432 59.051 88.05015 62.326 69.9320 1180361.17 1e+05





                                  share|improve this answer















                                  This seems nice,



                                  unlist(strsplit(mystring, split = ":", fixed=TRUE))[c(TRUE, FALSE,FALSE)]


                                  (Made with help from here)



                                  Alternative could be,



                                  sapply(strsplit(mystring, split=':', fixed=TRUE), `[`, 1)


                                  Using some benchmarks and recent comments by Ronak, that fixed=TRUE makes the methods a lot faster, we see that method four (the above method) is fastest,



                                  mystring <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                                  "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                                  "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                                  "01/09/2019 10:52:20")

                                  microbenchmark(one = sapply(strsplit(mystring, split=':', fixed=TRUE), `[`, 1),
                                  two = unlist(lapply(mystring,function(x) strsplit(x,":", fixed=TRUE)[[1]][1])),
                                  three = strptime(mystring, "%m/%d/%Y %H"),
                                  four = unlist(strsplit(mystring, split = ":", fixed=TRUE))[c(TRUE, FALSE,FALSE)],
                                  five = format(as.POSIXct(mystring, format = "%d/%m/%Y %H:%M:%OS"), "%d/%m/%Y %H"),
                                  six = gsub("(.*?):.*", "\1", mystring),
                                  seven = str_extract(mystring, ".+(?=:.+:)"),
                                  times = 100000)



                                  Unit: microseconds
                                  expr min lq mean median uq max neval
                                  one 42.792 49.471 85.63742 52.572 57.1310 669280.96 1e+05
                                  two 64.637 70.618 114.16364 73.252 77.6840 582466.94 1e+05
                                  three 129.456 134.771 156.82308 136.188 139.2030 339715.94 1e+05
                                  four 12.860 15.641 22.75699 17.254 18.5440 305703.52 1e+05
                                  five 482.888 505.647 633.15388 512.880 552.1155 551274.28 1e+05
                                  six 37.889 43.121 52.79030 45.567 49.1880 32954.59 1e+05
                                  seven 53.432 59.051 88.05015 62.326 69.9320 1180361.17 1e+05






                                  share|improve this answer














                                  share|improve this answer



                                  share|improve this answer








                                  edited Mar 22 at 12:59

























                                  answered Mar 21 at 1:17









                                  Hector HaffendenHector Haffenden

                                  501114




                                  501114












                                  • yep. I think fixed = TRUE makes it a lot faster.

                                    – Ronak Shah
                                    Mar 21 at 1:40






                                  • 1





                                    Very interesting, actually 4, with fixed=TRUE is fastest, changed the benchmark to show this.

                                    – Hector Haffenden
                                    Mar 21 at 1:43


















                                  • yep. I think fixed = TRUE makes it a lot faster.

                                    – Ronak Shah
                                    Mar 21 at 1:40






                                  • 1





                                    Very interesting, actually 4, with fixed=TRUE is fastest, changed the benchmark to show this.

                                    – Hector Haffenden
                                    Mar 21 at 1:43

















                                  yep. I think fixed = TRUE makes it a lot faster.

                                  – Ronak Shah
                                  Mar 21 at 1:40





                                  yep. I think fixed = TRUE makes it a lot faster.

                                  – Ronak Shah
                                  Mar 21 at 1:40




                                  1




                                  1





                                  Very interesting, actually 4, with fixed=TRUE is fastest, changed the benchmark to show this.

                                  – Hector Haffenden
                                  Mar 21 at 1:43






                                  Very interesting, actually 4, with fixed=TRUE is fastest, changed the benchmark to show this.

                                  – Hector Haffenden
                                  Mar 21 at 1:43












                                  0














                                  Another one:



                                  dates <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                                  "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                                  "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                                  "01/09/2019 10:52:20")
                                  unlist(lapply(dates,function(x) strsplit(x,":")[[1]][1]))


                                  gives



                                   [1] "01/09/2019 9" "01/09/2019 9" "01/09/2019 9" "01/09/2019 10" "01/09/2019 10"
                                  [6] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"





                                  share|improve this answer



























                                    0














                                    Another one:



                                    dates <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                                    "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                                    "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                                    "01/09/2019 10:52:20")
                                    unlist(lapply(dates,function(x) strsplit(x,":")[[1]][1]))


                                    gives



                                     [1] "01/09/2019 9" "01/09/2019 9" "01/09/2019 9" "01/09/2019 10" "01/09/2019 10"
                                    [6] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"





                                    share|improve this answer

























                                      0












                                      0








                                      0







                                      Another one:



                                      dates <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                                      "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                                      "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                                      "01/09/2019 10:52:20")
                                      unlist(lapply(dates,function(x) strsplit(x,":")[[1]][1]))


                                      gives



                                       [1] "01/09/2019 9" "01/09/2019 9" "01/09/2019 9" "01/09/2019 10" "01/09/2019 10"
                                      [6] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"





                                      share|improve this answer













                                      Another one:



                                      dates <- c("01/09/2019 9:51:03", "01/09/2019 9:51:39", "01/09/2019 9:57:04", 
                                      "01/09/2019 10:01:41", "01/09/2019 10:06:06", "01/09/2019 10:09:36",
                                      "01/09/2019 10:11:55", "01/09/2019 10:21:15", "01/09/2019 10:21:39",
                                      "01/09/2019 10:52:20")
                                      unlist(lapply(dates,function(x) strsplit(x,":")[[1]][1]))


                                      gives



                                       [1] "01/09/2019 9" "01/09/2019 9" "01/09/2019 9" "01/09/2019 10" "01/09/2019 10"
                                      [6] "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10" "01/09/2019 10"






                                      share|improve this answer












                                      share|improve this answer



                                      share|improve this answer










                                      answered Mar 21 at 1:16









                                      CIAndrewsCIAndrews

                                      55849




                                      55849





















                                          0














                                          Here is another one using gsub



                                          Capture the pattern by () and \1 to refer to the captured group, need ?to make regex lazy as there are multiple :.



                                          gsub("(.*?):.*", "\1", dates)





                                          share|improve this answer























                                          • Added to my benchmarking answer, hope thats okay.

                                            – Hector Haffenden
                                            Mar 21 at 2:17












                                          • All good, its great to see those benchmarks.

                                            – MKa
                                            Mar 21 at 2:55















                                          0














                                          Here is another one using gsub



                                          Capture the pattern by () and \1 to refer to the captured group, need ?to make regex lazy as there are multiple :.



                                          gsub("(.*?):.*", "\1", dates)





                                          share|improve this answer























                                          • Added to my benchmarking answer, hope thats okay.

                                            – Hector Haffenden
                                            Mar 21 at 2:17












                                          • All good, its great to see those benchmarks.

                                            – MKa
                                            Mar 21 at 2:55













                                          0












                                          0








                                          0







                                          Here is another one using gsub



                                          Capture the pattern by () and \1 to refer to the captured group, need ?to make regex lazy as there are multiple :.



                                          gsub("(.*?):.*", "\1", dates)





                                          share|improve this answer













                                          Here is another one using gsub



                                          Capture the pattern by () and \1 to refer to the captured group, need ?to make regex lazy as there are multiple :.



                                          gsub("(.*?):.*", "\1", dates)






                                          share|improve this answer












                                          share|improve this answer



                                          share|improve this answer










                                          answered Mar 21 at 1:56









                                          MKaMKa

                                          358412




                                          358412












                                          • Added to my benchmarking answer, hope thats okay.

                                            – Hector Haffenden
                                            Mar 21 at 2:17












                                          • All good, its great to see those benchmarks.

                                            – MKa
                                            Mar 21 at 2:55

















                                          • Added to my benchmarking answer, hope thats okay.

                                            – Hector Haffenden
                                            Mar 21 at 2:17












                                          • All good, its great to see those benchmarks.

                                            – MKa
                                            Mar 21 at 2:55
















                                          Added to my benchmarking answer, hope thats okay.

                                          – Hector Haffenden
                                          Mar 21 at 2:17






                                          Added to my benchmarking answer, hope thats okay.

                                          – Hector Haffenden
                                          Mar 21 at 2:17














                                          All good, its great to see those benchmarks.

                                          – MKa
                                          Mar 21 at 2:55





                                          All good, its great to see those benchmarks.

                                          – MKa
                                          Mar 21 at 2:55

















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