Problem with a for loop

Hello,

I have a four-dimensional matrix A(i,o,h,j) and I would like to find the mean of each j for each i,o,h. My goal is to get a tree-dimensional matrix B(i,o,h).

For example:

B(1,1,1)=(A(1,1,1,1)+A(1,1,1,2)+...+A(1,1,1,9))./9
B(150,12,7)=(A(150,12,7,1)+A(150,12,7,2)+...+A(150,12,7,9))./9

However this code below gives me a two 160x1 matrix. Any help would be much appreciated!

      l=160;  
      h=1;
      o=1;
      i=1;
      for h=1:12
          for o=1:12
              for i=i:l-o-h
                  B(i,o,h)=mean(A(i,o,h,:));
                  i=i+1;
              end
              o=o+1;
          end
          h=h+1;
      end

Answer 1

[Jonathan Sullivan]

It's much easier than this. The function mean allows you to specify a dimension over which to operate.

For you, you would want:

B = mean(A,4);

For more information, look at the documentation

help mean
doc mean

Answer 2

[Kevin]

      for h=1:size(A,3)
          for o=1:size(A,2)
              for i=1:size(A,1)
                  B(i,o,h)=mean(A(i,o,h,:),4);
              % (1) deleted your step fxn, matlab does this auto-magically
              end
           % (2) same as (1)
          end
          % (3) same as (1)
      end

This is the same effect as Jonathan's answer, but implemented as your for loop. Best of luck. KD

EDIT: For the record, Jon's is the way to do it...