How do you find the average of specific columns for all rows?

say like I have this 2D matrix

 1  2  3  4  5  6
 7  8  9 10 11 12
13 14 15 16 17 18
19 20 21 22 23 24

how do I find the average/mean for all of the rows but only for columns 1,2, and 6?

Answer 1

[Jos (10584)]

Select the columns, and then perform the operation:

A = magic(6)
B = A(:,[1 2 6])
meanVal = mean(B,2)

[Anonymous Matrix]

Thanks!