Find common rows in 2 different arrays (faster than ismember)

Hello everyone,

I am currently looking for a function that would return the index of identical row in 2 different array. I tried with

listIdx=ismember(conversion,x,"rows");

out=find(listIdx);

However it need a lot of time to get the result: ~0.7s 0.8s for 1 element when I can have more than 600 rows to compare.

I also trye ismembc function but it compare all the single elements of both array

Is there a faster way to that ?

Thank you in advance for your help

Mathieu

[Stephen23]

"Is there a faster way to that ?"

Perhaps one of these:

https://www.mathworks.com/matlabcentral/fileexchange?q=ismember

e.g.:

https://www.mathworks.com/matlabcentral/fileexchange/180-ismemberrows

[Dyuman Joshi]

You can replace find() by logical indexing, as using find() is a bit slower -

in=1:size(conversion,1);
listIdx=ismember(conversion,x,"rows");
out=in(listIdx)

If this doesn't improve the speed upto the level you desire, please attach your files, so that we can test run code and suggest a solution.

Edit - @Stephen23's suggestion to use ismemberrows from FEX seems to be a great option.

[Mathieu Chêne]

Thank you for your help,

I tryed to use IsMemberRows however even when the dll and the ;m file are in the same folder I have the following error : "Execution of script IsMemberRows as a function is not supported:"

I attached a script with the function , conversion ans x data (in tofind and tofind682 mat files).

@Dyuman Joshi Find() is not the problem here, most of the processing time is used by ismember.

[Stephen23]

"Execution of script IsMemberRows as a function is not supported"

Aaah, apparently the author of that FEX submssion uploaded a compiled DLL file. Not optimal:

https://www.mathworks.com/matlabcentral/answers/219681-link-dll-files-with-matlab

Usually the author provides code that is compiled on your machine. Perhaps this will help with the DLL:

https://www.mathworks.com/help/matlab/ref/loadlibrary.html

[Mathieu Chêne]

Ok I did not know that.

However when I try to load the .dll file like this :

loadlibrary('IsMemberRows.dll')

I have the following error

Unrecognized function or variable 'IsMemberRows_proto'.

Maybe I am doing something wrong because I have all the downloaded files in the same folder

[Stephen23]

"Maybe I am doing something wrong because I have all the downloaded files in the same folder"

No, I don't think you are doing anything wrong: the chance that a DLL created 23 years ago will run on your computer is slim. Unless someone knows how to make it work, we should consider that FEX submission as abandoned.