when doing A(B)=C, get average C values if index is used >1 times

say I have matrices

A = [0 0 0]
B=[1 1 2 3]
C=[10 20 30 40]

conventionally when doing

A(B)=C

I get

A = [20 30 40]

So by having a repeating index in B, the lowermost occurence of the index is uesd.

now what I need in this case is to get

A= [mean(C(1),C(2)) C(3) C(4)]

or alternatively another function such as min, max, etc.

So basically what I need is instead of always getting the last called index I need a function of all same called indices.

hope its possible to understand my problem. the real data i have is much bigger and the indices change iteratively, thus manually writing what I need is no option.

thanks for any help!

Answer 1

[Walter Roberson]

See findgroups and splitapply

Caution: if you are using a function that operates along the first non-singular dimension, such as mean() does, then be sure to specify the dimension at the time of calling the function if you are expecting to work by columns . mean() of a N x M matrix is 1 x M unless N == 1 in which case that is mean() of a vector and would return a scalar...

[Daniel Neubauer]

this looks exactly like what I need - thanks a lot!