CODEWITHSUNDEEP
matlab
Isak T.
Isak T.

Reputation: 345

Matrix containing integers instead of doubles in Matlab

I have a large vector containing integers (length: 230 400, int8) which I rearrange into a 3-dimensional matrix (rows: 240, cols: 320, depth: 3). When this has been done the new matrix contains doubles instead of ints (according to Matlab Workspace).

The whole operation takes 0.3 seconds, which is to long for my purposes.

Is Matlab converting the ints in the array to doubles before putting them in the matrix? Can this be avoided to speed it up?

Some code:

   tic;
   A=zeros(240,320,3);
   %A is matrix, B is vector.

   for i=1:240
       for j=1:320
           A(i,j,:)=B(1+(j-1)*3+(i-1)*320*3:3+(j-1)*3+(i-1)*320*3);
       end
   end

   toc;

Thanks!

Upvotes: 1

Views: 2202

Answers (2)

Jonas
Jonas

Reputation: 74940

Just use reshape on B. This is faster and will preserve the class of B.

A = reshape(B,[3,320,240]); %# makes a 3-by-320-by-240 array and distributes elements of B
A = permute(A,[3 2 1]);     %# turns A into a 240-by-320-by-3 array

Upvotes: 7

zellus
zellus

Reputation: 9592

Try initializing your matrix with

A=zeros(240, 320, 3, 'int8')

Upvotes: 2

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