Subscripted assignment dimension mismatch.

Hello all,

I know this is a common error and their seem to be millions of solutions for it however I can't get my code to run. I have read all the example I can find but non seem to help. this is my code:

a1=imread('1V.png'); a2=imread('2V.png'); a3=imread('3V.png'); a(:,:,1)=a1; a(:,:,2)=a2; a(:,:,3)=a3;

for t=1:3; y=a(:,:,t); Isum=sum(y,1); [Imax, Iloc]=max(Isum); I(t)=y(:,Iloc); end

The code runs fine if I place a single value in for t, however when I run it as a loop the subscript dimensions mismatch error pops up. I want the code to give me a matrix containing all of the I values, three columns in this case.

Answer 1

[KL]

imread returns a 3D matrix. If you want to read multiple images and store them in one matrix, use a 4D matrix,

 for k = 1:3
    a(:,:,:,k) = imread([num2str(k) 'V.png']);
    %other code
 end

[Robbie McDermott]

Thank you for your reply!

The code tells me that the imaread matrices are all 2D though. When I say size(a1) it returns 1280 960

[KL]

Aha, then you're reading grayscale images. The the problem should be in assiging l(t). Change it to l(:,t)

You've been actually trying to assign a vector to a single element. Alternative is to use cell arrays. l{t}.

[Robbie McDermott]

AH! Using l(:,t) has fixed it! Thank you very very much! that will save me a lot of time!

Thank you so much, very very much appreciated!!

[KL]

You're very welcome!

Another tip: Always try to preallocate your matrices before loop, this would greatly improve your code's performance. For example,

 l = zeros(256,3);