I have a vector of zeros, say of length 10. So
v = rep(0,10)
I want to populate some values of the vector, on the basis of a set of indexes in v1 and another vector v2 that actually has the values in sequence. So another vector v1 has the indexes say
v1 = c(1,2,3,7,8,9)
and
v2 = c(0.1,0.3,0.4,0.5,0.1,0.9)
In the end I want
v = c(0.1,0.3,0.4,0,0,0,0.5,0.1,0.9,0)
So the indexes in v1 got mapped from v2 and the remaining ones were 0. I can obviously write a for loop but thats taking too long in R, owing to the length of the actual matrices. Any simple way to do this?
Answer
You can assign it this way:
v[v1] = v2
For example:
> v = rep(0,10)
> v1 = c(1,2,3,7,8,9)
> v2 = c(0.1,0.3,0.4,0.5,0.1,0.9)
> v[v1] = v2
> v
[1] 0.1 0.3 0.4 0.0 0.0 0.0 0.5 0.1 0.9 0.0