Styjun

Are the requirements of a Horn of Valhalla cumulative?

What verb for taking advantage fits in "I don't want to ________ on the friendship"?

What is an example of of idiomatic "typed" WolframScript?

Most elegant way to write a one-shot 'if'

Is Cyclic Ether oxidised by periodic acid

What's the safest way to inform a new user of their password on an invite-only website?

Can I travel from Germany to England alone as an unaccompanied minor?

What is "oversubscription" in Networking?

SRAM Twist Shifter Paired with Shimano Rear Derailleur

What kind of jet plane is this?

Put my student loan in parents’ second mortgage - help?

How do I organize members in a struct to waste the least space on alignment?

The warming up game

Are gliders susceptible to bird strikes?

How do I tell the reader that my character is autistic in Fantasy?

Security Patch SUPEE-11155 - Possible issues?

Is it okay to submit a paper from a master's thesis without informing the advisor?

Which is better for keeping data: primary partition or logical partition?

13th chords on guitar

Why did NASA wet the road in front of the Space Shuttle crawler?

Find the radius of the hoop.

Why would anyone even use a Portkey?

How to describe POV characters?

Just graduated with a master’s degree, but I internalised nothing

Julia: vectorized version of searchsorted

Linking R and Julia?Initialize an Empty Array of Tuples in JuliaPython None and numpy commands in JuliaSapply (from R) equivalent for Julia?How do I change the data type of a Julia array from “Any” to “Float64”?Julia equivalent of R's paste() functionVector of matrices in Juliasorted indexes in Julia (equivalent to numpy's argsort)Calling a Julia 0.4 function from Python. How i can make it work?Why have “clamp”, “clamp.”, and “clamp!” in Julia?

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;

2

For each value in array B, how to find the closest value in array A with one function call, similar to how searchsorted(A, B) works in numpy.

julia

share|improve this question

edited Mar 25 at 14:45

user3055163

asked Mar 25 at 14:15

user3055163user3055163

14688 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  You've received two good answers. I just wanted to point out that if B is sorted and (approximately) larger than 0.1*length(A), then you will get better performance with an algorithm that performs a single simultaneous loop over A and B. The single loop over both ends up having less operations than length(B) binary chops, which is what broadcasting over searchsortedfirst will do.
  
  – Colin T Bowers
  Mar 25 at 23:26
  
  

  
  
  
  

add a comment | 

2

For each value in array B, how to find the closest value in array A with one function call, similar to how searchsorted(A, B) works in numpy.

julia

share|improve this question

edited Mar 25 at 14:45

user3055163

asked Mar 25 at 14:15

user3055163user3055163

14688 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  You've received two good answers. I just wanted to point out that if B is sorted and (approximately) larger than 0.1*length(A), then you will get better performance with an algorithm that performs a single simultaneous loop over A and B. The single loop over both ends up having less operations than length(B) binary chops, which is what broadcasting over searchsortedfirst will do.
  
  – Colin T Bowers
  Mar 25 at 23:26
  
  

  
  
  
  

add a comment | 

For each value in array B, how to find the closest value in array A with one function call, similar to how searchsorted(A, B) works in numpy.

julia

share|improve this question

edited Mar 25 at 14:45

user3055163

asked Mar 25 at 14:15

user3055163user3055163

14688 bronze badges

share|improve this question

edited Mar 25 at 14:45

user3055163

asked Mar 25 at 14:15

user3055163user3055163

14688 bronze badges

share|improve this question

edited Mar 25 at 14:45

user3055163

asked Mar 25 at 14:15

user3055163user3055163

14688 bronze badges

asked Mar 25 at 14:15

user3055163user3055163

14688 bronze badges

asked Mar 25 at 14:15

user3055163user3055163

14688 bronze badges

2 Answers
2

active

oldest

votes

2

searchsortedfirst.(Ref(A),B)

should give you the desired result. Example:

julia> A = [1, 2, 2, 4, 4, 4, 4, 4, 9, 10];

julia> B = [10, 6, 9];

julia> searchsortedfirst.(Ref(A), B)
3-element ArrayInt64,1:
 10
 9
 9

Compare to np.searchsorted:

julia> using PyCall

julia> np = pyimport("numpy");

julia> np.searchsorted(A,B)
3-element ArrayInt64,1:
 9
 8
 8

which (up to Python's 0-based indexing) is equivalent.

Explanation:
What does searchsortedfirst.(Ref(A),B) do?

The dot tells Julia to broadcast the searchsortedfirst call. However, we have to make sure that A is still treated as an array in each call (we want A to be a scalar under broadcasting). This can be achieved by wrapping A in a Ref.

share|improve this answer

answered Mar 25 at 14:28

crstnbrcrstnbr

4,73811 gold badge1212 silver badges2525 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Spot on. Thank you very much.
  
  – user3055163
  Mar 25 at 14:30
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is a correct equivalent of numpy code, but please note (I was writing the answer in parallel) that the numpy code does not find what you want. In particular searchsortedfirst can return you out-of-bounds index.
  
  – Bogumił Kamiński
  Mar 25 at 14:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Haven't you interchanged A and B here? At least according to the explanation in the question?
  
  – DNF
  Mar 25 at 14:44
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  My question was misleading. I've corrected it.
  
  – user3055163
  Mar 25 at 14:46
  

  
  
  
  

add a comment | 

1

Assuming B is unsorted (but then you cannot use searchsorted in numpy either) you can do:

[argmin(abs(a .- B)) for a in A]

If B is sorted and you accept that you do not find the closest value in array B (searchsorted does not find the closest value) you can write:

searchsorted.(Ref(B), A)

and you will get ranges in which elements of A sould be placed in B (you can also checkout functions searchsortedfirst and searchsortedlast)

share|improve this answer

answered Mar 25 at 14:31

Bogumił KamińskiBogumił Kamiński

17.9k22 gold badges1818 silver badges2626 bronze badges

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%2f55339848%2fjulia-vectorized-version-of-searchsorted%23new-answer', 'question_page');

);

Post as a guest

Name

Email

Required, but never shown

2

searchsortedfirst.(Ref(A),B)

should give you the desired result. Example:

julia> A = [1, 2, 2, 4, 4, 4, 4, 4, 9, 10];

julia> B = [10, 6, 9];

julia> searchsortedfirst.(Ref(A), B)
3-element ArrayInt64,1:
 10
 9
 9

Compare to np.searchsorted:

julia> using PyCall

julia> np = pyimport("numpy");

julia> np.searchsorted(A,B)
3-element ArrayInt64,1:
 9
 8
 8

which (up to Python's 0-based indexing) is equivalent.

Explanation:
What does searchsortedfirst.(Ref(A),B) do?

The dot tells Julia to broadcast the searchsortedfirst call. However, we have to make sure that A is still treated as an array in each call (we want A to be a scalar under broadcasting). This can be achieved by wrapping A in a Ref.

share|improve this answer

answered Mar 25 at 14:28

crstnbrcrstnbr

4,73811 gold badge1212 silver badges2525 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Spot on. Thank you very much.
  
  – user3055163
  Mar 25 at 14:30
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is a correct equivalent of numpy code, but please note (I was writing the answer in parallel) that the numpy code does not find what you want. In particular searchsortedfirst can return you out-of-bounds index.
  
  – Bogumił Kamiński
  Mar 25 at 14:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Haven't you interchanged A and B here? At least according to the explanation in the question?
  
  – DNF
  Mar 25 at 14:44
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  My question was misleading. I've corrected it.
  
  – user3055163
  Mar 25 at 14:46
  

  
  
  
  

add a comment | 

2

searchsortedfirst.(Ref(A),B)

should give you the desired result. Example:

julia> A = [1, 2, 2, 4, 4, 4, 4, 4, 9, 10];

julia> B = [10, 6, 9];

julia> searchsortedfirst.(Ref(A), B)
3-element ArrayInt64,1:
 10
 9
 9

Compare to np.searchsorted:

julia> using PyCall

julia> np = pyimport("numpy");

julia> np.searchsorted(A,B)
3-element ArrayInt64,1:
 9
 8
 8

which (up to Python's 0-based indexing) is equivalent.

Explanation:
What does searchsortedfirst.(Ref(A),B) do?

The dot tells Julia to broadcast the searchsortedfirst call. However, we have to make sure that A is still treated as an array in each call (we want A to be a scalar under broadcasting). This can be achieved by wrapping A in a Ref.

share|improve this answer

answered Mar 25 at 14:28

crstnbrcrstnbr

4,73811 gold badge1212 silver badges2525 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Spot on. Thank you very much.
  
  – user3055163
  Mar 25 at 14:30
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is a correct equivalent of numpy code, but please note (I was writing the answer in parallel) that the numpy code does not find what you want. In particular searchsortedfirst can return you out-of-bounds index.
  
  – Bogumił Kamiński
  Mar 25 at 14:32
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Haven't you interchanged A and B here? At least according to the explanation in the question?
  
  – DNF
  Mar 25 at 14:44
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  My question was misleading. I've corrected it.
  
  – user3055163
  Mar 25 at 14:46
  

  
  
  
  

add a comment | 

searchsortedfirst.(Ref(A),B)

should give you the desired result. Example:

julia> A = [1, 2, 2, 4, 4, 4, 4, 4, 9, 10];

julia> B = [10, 6, 9];

julia> searchsortedfirst.(Ref(A), B)
3-element ArrayInt64,1:
 10
 9
 9

Compare to np.searchsorted:

julia> using PyCall

julia> np = pyimport("numpy");

julia> np.searchsorted(A,B)
3-element ArrayInt64,1:
 9
 8
 8

which (up to Python's 0-based indexing) is equivalent.

Explanation:
What does searchsortedfirst.(Ref(A),B) do?

The dot tells Julia to broadcast the searchsortedfirst call. However, we have to make sure that A is still treated as an array in each call (we want A to be a scalar under broadcasting). This can be achieved by wrapping A in a Ref.

share|improve this answer

answered Mar 25 at 14:28

crstnbrcrstnbr

4,73811 gold badge1212 silver badges2525 bronze badges

searchsortedfirst.(Ref(A),B)

julia> A = [1, 2, 2, 4, 4, 4, 4, 4, 9, 10];

julia> B = [10, 6, 9];

julia> searchsortedfirst.(Ref(A), B)
3-element ArrayInt64,1:
 10
 9
 9

julia> using PyCall

julia> np = pyimport("numpy");

julia> np.searchsorted(A,B)
3-element ArrayInt64,1:
 9
 8
 8

share|improve this answer

answered Mar 25 at 14:28

crstnbrcrstnbr

4,73811 gold badge1212 silver badges2525 bronze badges

answered Mar 25 at 14:28

crstnbrcrstnbr

4,73811 gold badge1212 silver badges2525 bronze badges

answered Mar 25 at 14:28

crstnbrcrstnbr

4,73811 gold badge1212 silver badges2525 bronze badges

1

Assuming B is unsorted (but then you cannot use searchsorted in numpy either) you can do:

[argmin(abs(a .- B)) for a in A]

If B is sorted and you accept that you do not find the closest value in array B (searchsorted does not find the closest value) you can write:

searchsorted.(Ref(B), A)

and you will get ranges in which elements of A sould be placed in B (you can also checkout functions searchsortedfirst and searchsortedlast)

share|improve this answer

answered Mar 25 at 14:31

Bogumił KamińskiBogumił Kamiński

17.9k22 gold badges1818 silver badges2626 bronze badges

add a comment | 

1

Assuming B is unsorted (but then you cannot use searchsorted in numpy either) you can do:

[argmin(abs(a .- B)) for a in A]

If B is sorted and you accept that you do not find the closest value in array B (searchsorted does not find the closest value) you can write:

searchsorted.(Ref(B), A)

and you will get ranges in which elements of A sould be placed in B (you can also checkout functions searchsortedfirst and searchsortedlast)

share|improve this answer

answered Mar 25 at 14:31

Bogumił KamińskiBogumił Kamiński

17.9k22 gold badges1818 silver badges2626 bronze badges

add a comment | 

Assuming B is unsorted (but then you cannot use searchsorted in numpy either) you can do:

[argmin(abs(a .- B)) for a in A]

If B is sorted and you accept that you do not find the closest value in array B (searchsorted does not find the closest value) you can write:

searchsorted.(Ref(B), A)

and you will get ranges in which elements of A sould be placed in B (you can also checkout functions searchsortedfirst and searchsortedlast)

share|improve this answer

answered Mar 25 at 14:31

Bogumił KamińskiBogumił Kamiński

17.9k22 gold badges1818 silver badges2626 bronze badges

[argmin(abs(a .- B)) for a in A]

searchsorted.(Ref(B), A)

share|improve this answer

answered Mar 25 at 14:31

Bogumił KamińskiBogumił Kamiński

17.9k22 gold badges1818 silver badges2626 bronze badges

answered Mar 25 at 14:31

Bogumił KamińskiBogumił Kamiński

17.9k22 gold badges1818 silver badges2626 bronze badges

answered Mar 25 at 14:31

Bogumił KamińskiBogumił Kamiński

17.9k22 gold badges1818 silver badges2626 bronze badges