[R] distance between two matrices

["Jens Oehlschlägel"]

Sundar,

Have a look at "knn1" from package "class".

As I understand what you want is

as.integer( knn1(train=A, test=B, cl=1:nrow(A)) )


Best regards


Jens Oehlschlägel


>   Say I have a matrix A with dimension m x 2 and matrix B with 
> dimension n x 2. I would like to find the row in A that is closest to 
> the each row in B. Here's an example (using a loop):

> set.seed(1)
> A <- matrix(runif(12), 6, 2) # 6 x 2
> B <- matrix(runif(6), 3, 2)  # 3 x 2
> m <- vector("numeric", nrow(B))
> for(j in 1:nrow(B)) {
>    d <- (A[, 1] - B[j, 1])^2 + (A[, 2] - B[j, 2])^2
>    m[j] <- which.min(d)
> }

> All I need is m[]. I would like to accomplish this without using the 
> loop if possible, since for my real data n > 140K and m > 1K. I hope 
> this makes sense.



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