Loop help

hi, I have two columns of data. Column 1 just contains the numbers 1, 2 and 3 in no particular order and column 2 contains data points that correspond to the numbers 1,2 and 3 in column one. The data is arranged in ascending order by column one. I want to write a simple loop that groups the 1's together and calculates the mean of the corresponding values in column 2 and does the same same for 2's and the 3's. I just need some help in writing this loop. Thanks.

Answer 1

[Sean de Wolski]

No reason for a for-loop:

X = [ceil(rand(10,1)*3) (1:10).']; %two column matrix of 1:3 in first column and values in second
group_means = accumarray(X(:,1),X(:,2),[],@mean); %mean grouped by first column

And of course:

doc accumarray

[Syed Abbas]

Thanks - much simpler