change matrix from 3D TO 2D

i have 3d matrix (512x512x3) i want transform to 2d matrix (512x512)

[Mattias Gothberg]

check out squeeze comand after apropiate processing or selection

Answer 1

[Thomas]

Your matrix has 512*512*3=786432 elements.. to reshape you need to keep the number of elements the same.. That means you cannot reshape if you want just 512*512 elements without losing elements or data..

However if you want to access only the first dimension of your matrix (a) you use some thing like a(:,:,1)

If your data is an image data and it has the three dimension r,g,b you can covert it to grayscale (using im2bw)which should give you a matrix of 512*512

Example for my color image 1.jpg

ii=imread('1.jpg');
size(ii)

ans =
        551.00       1024.00          3.00

out=im2bw(ii);   % convert to blackwhite
size(out)

ans =
        551.00       1024.00

Answer 2

[Wayne King]

You have to select one "page" of the 3D matrix, which one do you want?

   X = randn(512,512,3);
   Y = X(:,:,1);

Or you can form some function of the 3 pages, not sure what you want. For example:

   X = randn(512,512,3);
   Y = mean(X,3);