How to calculate single average of all rows and single average of all columns of image?

I am having a gray image of size 256 by 256 and want to calculate row and column mean. I am able to calculate column mean of image as follow im=imread('E:\xyz.jpg') cmean=mean(mean(im)); In order to take row mean I took transpose of im matrix and then calculated the mean. im1 = transpose(im); rmean=mean(mean(im1));

Column and row mean should be different. But gives the same answer for row and column mean. What is wrong?

Answer 1

[Jan]

As explained in the documentation of doc mean, the dimension to operate on can be defined by the second input:

x = rand(10, 10);
m_dim1 = mean(x, 1);
m_dim2 = mean(x, 2);

If mean(X) and mean(X.') reply the same values, either X is a vector or the means are equal. mean(X) without specifying the dimension operates on the first non-singelton dimension. This is risky: You save half a second during typing, but might spend hours with debugging. So prefer to define the dimension explicitly, because sometime Matlab's smart decisions to guess what you want, are too smart.

[anu]

Your solution is working. But when I applied my solution for following example, its working properly.

A = [0 1 1; 2 3 2; 1 3 2; 4 2 2]

A =

     0     1     1
     2     3     2
     1     3     2
     4     2     2

 mean(A)

ans =

    1.7500    2.2500    1.7500

>> B=transpose(A)

B =

     0     2     1     4
     1     3     3     2
     1     2     2     2

>> mean(B)

ans =

    0.6667    2.3333    2.0000    2.6667

But when applied to image matrix not working properly. why?