Styjun

What standard algorithm can determine if exactly one of a container satisfies a predicate?

Russian word for a male zebra

60s or 70s novel about Empire of Man making 1st contact with 1st discovered alien race

How creative should the DM let an artificer be in terms of what they can build?

Should I refuse being named as co-author of a bad quality paper?

How do free-speech protections in the United States apply in public to corporate misrepresentations?

How can one's career as a reviewer be ended?

Can the removal of a duty-free sales trolley result in a measurable reduction in emissions?

Why am I getting a strange double quote (“) in Open Office instead of the ordinary one (")?

Insert external file and modify each line from script

What is the logic behind taxing money for property?

Ability To Change Root User Password (Vulnerability?)

I have a problematic assistant manager, but I can't fire him

How can I remove material from this wood beam?

Increase speed altering column on large table to NON NULL

The Frozen Wastes

Next date with distinct digits

What are some really overused phrases in French that are common nowadays?

Is it possible for a vehicle to be manufactured without a catalytic converter?

Electricity free spaceship

Is there a DSLR/mirorless camera with minimal options like a classic, simple SLR?

Will Roalesk, Apex Hybrid, trigger Sharktocrab twice?

Did Apple bundle a specific monitor with the Apple II+ for schools?

Can a human be transformed into a Mind Flayer?

How to reproduce image using writeJPEG from the mean of all elements in a nested array in R

convert list to a matrix or array?How can I remove an element from a list?How do I install an R package from source?How to find common elements from multiple vectors?How to make a great R reproducible exampleHow can I remove all objects but one from the workspace in R?How to save a plot as image on the disk?Reproduce table and plot from journalSelect first element of nested listMean of all means of subsets of data differs from overall meanHow to calculate the mean by index of N elements in an array in R

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty height:90px;width:728px;box-sizing:border-box;

1

1

I have a nested array with a complicated structure. This array is a collection of 15 people, each with 11 images taken portraying 11 facial expressions such as wink, happy, etc.

I would like to calculate the mean images of 15 people with their 11 images taken.

The structure of all.faces is:

> str(all.faces)
List of 165
 $ : int [1:159, 1:159] 48 50 51 50 50 53 57 55 50 47 ...
 $ : int [1:159, 1:159] 159 156 131 130 117 115 122 119 123 129 ...
 (... and 163 more...)
 [list output truncated]
 - attr(*, "dim")= int [1:2] 11 15
 - attr(*, "dimnames")=List of 2
 ..$ : chr [1:11] "centerlight" "glasses" "happy" "leftlight" ...
 ..$ : NULL

When I tried

myarray <- array(as.numeric(unlist(faces)), dim=c(159, 159, 15))

mean.faces <- apply(myarray,1:2, mean)
writeJPEG(mean.faces,"MEAN_FACES.jpg")

I got this:

How come? I would assume that I would some sort of image, not a mess of black and white color scheme like this.

Reproducible example

faces <- readMat("https://github.com/angelleng/545dump/blob/master/yalefaces.mat?raw=true")
faces.array <- array(as.numeric(unlist(faces)), dim=c(159, 159, 15))

mean.all.faces <- apply(faces.array,1:2, mean)
writeJPEG(mean.all.faces,"MEAN_FACES.jpg")

What is the best way to approach this situation?

Thanks in advance.

r computation

share|improve this question

edited Mar 24 at 21:20

Adam Ralphus

asked Mar 24 at 19:54

Adam RalphusAdam Ralphus

11410

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Your apply would work, except that would require your data to be in an 3d array, not a list.
  
  – Axeman
  Mar 24 at 19:56
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Axeman How can I handle this case with a list?
  
  – Adam Ralphus
  Mar 24 at 19:57
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @AdamRalphus See if this helps stackoverflow.com/a/37436412/6574038
  
  – jay.sf
  Mar 24 at 19:59
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @jay.sf I updated my post.
  
  – Adam Ralphus
  Mar 24 at 20:18
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Can you share a minimal reproducible example?
  
  – markus
  Mar 24 at 20:27
  

  
  
  
  

 | 
show 1 more comment

1

1

I have a nested array with a complicated structure. This array is a collection of 15 people, each with 11 images taken portraying 11 facial expressions such as wink, happy, etc.

I would like to calculate the mean images of 15 people with their 11 images taken.

The structure of all.faces is:

> str(all.faces)
List of 165
 $ : int [1:159, 1:159] 48 50 51 50 50 53 57 55 50 47 ...
 $ : int [1:159, 1:159] 159 156 131 130 117 115 122 119 123 129 ...
 (... and 163 more...)
 [list output truncated]
 - attr(*, "dim")= int [1:2] 11 15
 - attr(*, "dimnames")=List of 2
 ..$ : chr [1:11] "centerlight" "glasses" "happy" "leftlight" ...
 ..$ : NULL

When I tried

myarray <- array(as.numeric(unlist(faces)), dim=c(159, 159, 15))

mean.faces <- apply(myarray,1:2, mean)
writeJPEG(mean.faces,"MEAN_FACES.jpg")

I got this:

How come? I would assume that I would some sort of image, not a mess of black and white color scheme like this.

Reproducible example

faces <- readMat("https://github.com/angelleng/545dump/blob/master/yalefaces.mat?raw=true")
faces.array <- array(as.numeric(unlist(faces)), dim=c(159, 159, 15))

mean.all.faces <- apply(faces.array,1:2, mean)
writeJPEG(mean.all.faces,"MEAN_FACES.jpg")

What is the best way to approach this situation?

Thanks in advance.

r computation

share|improve this question

edited Mar 24 at 21:20

Adam Ralphus

asked Mar 24 at 19:54

Adam RalphusAdam Ralphus

11410

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Your apply would work, except that would require your data to be in an 3d array, not a list.
  
  – Axeman
  Mar 24 at 19:56
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @Axeman How can I handle this case with a list?
  
  – Adam Ralphus
  Mar 24 at 19:57
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @AdamRalphus See if this helps stackoverflow.com/a/37436412/6574038
  
  – jay.sf
  Mar 24 at 19:59
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  @jay.sf I updated my post.
  
  – Adam Ralphus
  Mar 24 at 20:18
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Can you share a minimal reproducible example?
  
  – markus
  Mar 24 at 20:27
  

  
  
  
  

 | 
show 1 more comment

I have a nested array with a complicated structure. This array is a collection of 15 people, each with 11 images taken portraying 11 facial expressions such as wink, happy, etc.

I would like to calculate the mean images of 15 people with their 11 images taken.

The structure of all.faces is:

> str(all.faces)
List of 165
 $ : int [1:159, 1:159] 48 50 51 50 50 53 57 55 50 47 ...
 $ : int [1:159, 1:159] 159 156 131 130 117 115 122 119 123 129 ...
 (... and 163 more...)
 [list output truncated]
 - attr(*, "dim")= int [1:2] 11 15
 - attr(*, "dimnames")=List of 2
 ..$ : chr [1:11] "centerlight" "glasses" "happy" "leftlight" ...
 ..$ : NULL

When I tried

myarray <- array(as.numeric(unlist(faces)), dim=c(159, 159, 15))

mean.faces <- apply(myarray,1:2, mean)
writeJPEG(mean.faces,"MEAN_FACES.jpg")

I got this:

How come? I would assume that I would some sort of image, not a mess of black and white color scheme like this.

Reproducible example

faces <- readMat("https://github.com/angelleng/545dump/blob/master/yalefaces.mat?raw=true")
faces.array <- array(as.numeric(unlist(faces)), dim=c(159, 159, 15))

mean.all.faces <- apply(faces.array,1:2, mean)
writeJPEG(mean.all.faces,"MEAN_FACES.jpg")

What is the best way to approach this situation?

Thanks in advance.

r computation

share|improve this question

edited Mar 24 at 21:20

Adam Ralphus

asked Mar 24 at 19:54

Adam RalphusAdam Ralphus

11410

> str(all.faces)
List of 165
 $ : int [1:159, 1:159] 48 50 51 50 50 53 57 55 50 47 ...
 $ : int [1:159, 1:159] 159 156 131 130 117 115 122 119 123 129 ...
 (... and 163 more...)
 [list output truncated]
 - attr(*, "dim")= int [1:2] 11 15
 - attr(*, "dimnames")=List of 2
 ..$ : chr [1:11] "centerlight" "glasses" "happy" "leftlight" ...
 ..$ : NULL

myarray <- array(as.numeric(unlist(faces)), dim=c(159, 159, 15))

mean.faces <- apply(myarray,1:2, mean)
writeJPEG(mean.faces,"MEAN_FACES.jpg")

faces <- readMat("https://github.com/angelleng/545dump/blob/master/yalefaces.mat?raw=true")
faces.array <- array(as.numeric(unlist(faces)), dim=c(159, 159, 15))

mean.all.faces <- apply(faces.array,1:2, mean)
writeJPEG(mean.all.faces,"MEAN_FACES.jpg")

share|improve this question

edited Mar 24 at 21:20

Adam Ralphus

asked Mar 24 at 19:54

Adam RalphusAdam Ralphus

11410

share|improve this question

edited Mar 24 at 21:20

Adam Ralphus

asked Mar 24 at 19:54

Adam RalphusAdam Ralphus

11410

asked Mar 24 at 19:54

Adam RalphusAdam Ralphus

11410

asked Mar 24 at 19:54

Adam RalphusAdam Ralphus

11410

1 Answer
1

active

oldest

votes

1

Short answer: writeJPEG() needs a matrix of values between 0 and 1. You're giving it the raw data which has values in the range 0-255.

In detail, the example you gave (yalefaces.mat) has dimensions:

> faces <- readMat("https://github.com/angelleng/545dump/blob/master/yalefaces.mat?raw=true")
> dim(faces[[1]])
[1] 48 42 2414

so it's actually 2414 faces of size 48x42. We can display one like so:

> image(faces[[1]][,,1])

If you average them (without trying to resize the array, of course):

> mean.all.faces <- apply(faces[[1]], 1:2, mean)
> image(mean.all.faces)

it seems to work fine:

But when you write it out to a JPEG, the following will give garbage:

> writeJPEG(mean.all.faces, "BAD.jpg")

while the following works (though it's a little dark):

> writeJPEG(mean.all.faces/255, "GOOD.jpg")

share|improve this answer

answered Mar 24 at 21:30

K. A. BuhrK. A. Buhr

17.3k21638

add a comment | 

Your Answer

StackExchange.ifUsing("editor", function ()
StackExchange.using("externalEditor", function ()
StackExchange.using("snippets", function ()
StackExchange.snippets.init();
);
);
, "code-snippets");

StackExchange.ready(function()
var channelOptions =
tags: "".split(" "),
id: "1"
;
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function()
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled)
StackExchange.using("snippets", function()
createEditor();
);

else
createEditor();

);

function createEditor()
StackExchange.prepareEditor(
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader:
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
,
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
);



);

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);

Sign up using Google

Sign up using Facebook

Sign up using Email and Password

Post as a guest

Name

Email

Required, but never shown

StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f55327950%2fhow-to-reproduce-image-using-writejpeg-from-the-mean-of-all-elements-in-a-nested%23new-answer', 'question_page');

);

Post as a guest

Name

Email

Required, but never shown

1

Short answer: writeJPEG() needs a matrix of values between 0 and 1. You're giving it the raw data which has values in the range 0-255.

In detail, the example you gave (yalefaces.mat) has dimensions:

> faces <- readMat("https://github.com/angelleng/545dump/blob/master/yalefaces.mat?raw=true")
> dim(faces[[1]])
[1] 48 42 2414

so it's actually 2414 faces of size 48x42. We can display one like so:

> image(faces[[1]][,,1])

If you average them (without trying to resize the array, of course):

> mean.all.faces <- apply(faces[[1]], 1:2, mean)
> image(mean.all.faces)

it seems to work fine:

But when you write it out to a JPEG, the following will give garbage:

> writeJPEG(mean.all.faces, "BAD.jpg")

while the following works (though it's a little dark):

> writeJPEG(mean.all.faces/255, "GOOD.jpg")

share|improve this answer

answered Mar 24 at 21:30

K. A. BuhrK. A. Buhr

17.3k21638

add a comment | 

1

Short answer: writeJPEG() needs a matrix of values between 0 and 1. You're giving it the raw data which has values in the range 0-255.

In detail, the example you gave (yalefaces.mat) has dimensions:

> faces <- readMat("https://github.com/angelleng/545dump/blob/master/yalefaces.mat?raw=true")
> dim(faces[[1]])
[1] 48 42 2414

so it's actually 2414 faces of size 48x42. We can display one like so:

> image(faces[[1]][,,1])

If you average them (without trying to resize the array, of course):

> mean.all.faces <- apply(faces[[1]], 1:2, mean)
> image(mean.all.faces)

it seems to work fine:

But when you write it out to a JPEG, the following will give garbage:

> writeJPEG(mean.all.faces, "BAD.jpg")

while the following works (though it's a little dark):

> writeJPEG(mean.all.faces/255, "GOOD.jpg")

share|improve this answer

answered Mar 24 at 21:30

K. A. BuhrK. A. Buhr

17.3k21638

add a comment | 

Short answer: writeJPEG() needs a matrix of values between 0 and 1. You're giving it the raw data which has values in the range 0-255.

In detail, the example you gave (yalefaces.mat) has dimensions:

> faces <- readMat("https://github.com/angelleng/545dump/blob/master/yalefaces.mat?raw=true")
> dim(faces[[1]])
[1] 48 42 2414

so it's actually 2414 faces of size 48x42. We can display one like so:

> image(faces[[1]][,,1])

If you average them (without trying to resize the array, of course):

> mean.all.faces <- apply(faces[[1]], 1:2, mean)
> image(mean.all.faces)

it seems to work fine:

But when you write it out to a JPEG, the following will give garbage:

> writeJPEG(mean.all.faces, "BAD.jpg")

while the following works (though it's a little dark):

> writeJPEG(mean.all.faces/255, "GOOD.jpg")

share|improve this answer

answered Mar 24 at 21:30

K. A. BuhrK. A. Buhr

17.3k21638

> faces <- readMat("https://github.com/angelleng/545dump/blob/master/yalefaces.mat?raw=true")
> dim(faces[[1]])
[1] 48 42 2414

> image(faces[[1]][,,1])

> mean.all.faces <- apply(faces[[1]], 1:2, mean)
> image(mean.all.faces)

> writeJPEG(mean.all.faces, "BAD.jpg")

> writeJPEG(mean.all.faces/255, "GOOD.jpg")

share|improve this answer

answered Mar 24 at 21:30

K. A. BuhrK. A. Buhr

17.3k21638

answered Mar 24 at 21:30

K. A. BuhrK. A. Buhr

17.3k21638

answered Mar 24 at 21:30

K. A. BuhrK. A. Buhr

17.3k21638