Finding ALL the indicies that match a certain value

Suppose I have a variable A= 4

and I have a vector B = [ 3 5 4 6 4 6 7 ]

I want to find the index of B that match A

that is , a vector with [ 3 , 5 ] since they are the third and 5th

Answer 1

[Star Strider]

Use the find function:

A = 4; 
B = [ 3 5 4 6 4 6 7 ];
idx = find(B == A)

producing:

idx =
     3     5