How do I compute the mean value of odd rows of a random matrix (mxm)? (using if and rem)

First of all I already created a random matrix mxm using 'if', then compute the mean value for each columnn using 'for loop'. But now I got compute the mean value for odd rows using 'if' again, and the homework says 'use rem' as a hint.

Thanks in advance!

[dpb]

Sounds too suspiciously like homework...if so, we need to see whatyou've done on your own...and what the specific groundrules really are (are, in fact the above two mandated to be part of the solution)?

[JP Retaw]

In fact, they are. Before that I got do a random Matrix mxm using (if), then compute the mean value for all the columns using 'for loop'. And now they are asking for that.

Answer 1

[Jan]

I do not have any idea, how "if" can be used to produce a random matrix. But using REM() to get the odd indices is easy:

for k = 1:m
    if rem(k, 2) == 1
       meanValue = mean(X(k, :));
       % Now it is computed. POerhaps you want to store it in
       % an output?
    end
end

By the way, the matlabish way would be to omit the loops

meanVlaue = mean(X(1:2:end, :), 2)

Do you see the elegance? Your homework question asks you explicitly to use Matlab in an unefficient way. Therefore I've posted a solution, although it solves your homework.

[JP Retaw]

You rock!!, thank you so much, I really appreciate!