Replace certain elements of vector with the values from another vector (average the values belonging the same position)

If A = [0 0 0 0 0] and B = [5 6 4] and C = [2 5 2] then

how can I get average of two values ​​belong to position 2nd in final answer that menas final answer should like A = [0 4.5 0 0 6]?

Answer 1

[KSSV]

A = [0 0 0 0 0] ; 
B = [5 6 4] ;
C = [2 5 2] ; 
[c,ia,ib] = unique(C) ; 

for i = 1:length(c)
  A(C(ib==i)) = mean(B(ib==i)) ; 
end

[TAPAN PATEL]

thank you for the reply