Thread Subject: matrix labels for color segmentation

I have a MxNx3 matrix which is a color image.
Then I add a 4th column to be used as labeling index for segmentation.
I reshape this matrix to a MNx4 matrix where the first 3 columns are the 3 color components and the 4th column are the labels index.
I need to compute mean and cov of the pixels with assigned label.
I thought about scanning the matrix looking for the rows having as 4th value in the row the same number of the label index.

temp=zeros(1,4);
    for x = 1:3
        if (RGB_columns(x,4) == label)
            temp(x,:) = RGB_columns(x,:);
        end;
    end
MU = mean(temp(:,:));

In this way I should create the temp matrix with only the rows having the value that I am looking for in the label field...but I get this error message:
"Maximum recursion limit of 500 reached"
and if I change this value of course Matlab crashes.

Please consider this code instead of the previous posted.


    temp=zeros(HLS_RESHAPE_ROWS,HLS_RESHAPE_COLS);
    for x = 1:HLS_RESHAPE_ROWS
        if (HLS_RESHAPE(x,4) == label)
            temp(x,1:3) = HLS_RESHAPE(x,1:3);
        end;
    end
MU=mean(temp);

Thanks very much in advance to whom could help me.

solved...