[R] vectorizaton

[Liaw, Andy]

Try:

mymat <- rowMeans(P, dims=2)

Andy

> From: Dimitri Joe
> 
> Hi,
> 
> I got 1000 NxN matrices grouped in one array. I want one 
> matrix in which p_ij is the average of all the 1000 matrices 
> in the array. Here's what I'm trying to do:
> 
> # P is the NxNx1000 array
> 
> for(i in 1:N)
> for(j in 1:N)
> for(k in 1: 1000)
> mymat[ i, j ] <- mean( P [i , j , k ]  )
> 
> Otherwise, I could have a NxNx1000 vector, and get the N^2 
> means of the 1+ (N^2)*(0: 999) elements. I don't know which 
> is more efficient, but I wouldn't know how to carry this last 
> solution out anyway. Any ideas on how to do this efficiently?
> 
> Thanks,
> 
> Dimitri
> 	[[alternative HTML version deleted]]
> 
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