column-wise operation based on indices, accumarray?

if s and v are matrices of the same sizes.

s = [1 1

1 2

2 2

1 2

2 2

3 1

3 1];

v = [10 10

20 7

5 13

60 2

9 6

8 3

3 5];

For each column, find the mean of values of elements in matrix v with the same index in matrix s and replace the values with the mean.

m = [30 6

30 7

7 7

30 7

7 7

5.5 6

5.5 6]:

I know how to use unique and for loop to get the answer. I was wondering if there is a neater way.

Answer 1

[Walter Roberson]

accumarray(s(:, 1),v(:,1),[],@mean)

Now do that for each column.

Where I wrote [] use [max(s(:)), 1] . Note this is not max of the column, it is overall maximum.