[R] Common R/S Idioms - Swapping Rows or Cols in a Matrix

[Rob Lee]

Is there an idiomatic way of swapping rows/cols in a Matrix?

The standard approach for swapping rows r and u:
tmpRow = A[r,]
A[r,] = A[u,]
A[u,] = tmpRow

Robin Hankin (R-Octave help sheet maintainer) says:

[I would implement your three line solution (which works!) as follows:

swap <- function(a,m,n) {
 tmp <- a[m]
 a[m] <- a[n]
 a[n] <- tmp
 return(a)
}

then use things like

x <- matrix(1:100,10,10)

x[ swap(1:10,5,6),]                #swaps rows  5&6
x[,swap(1:10,5,6) ]                #swaps cols  5&6
x[ swap(1:10,5,6),swap(1:10,5,6)]  #both together

]

Anybody?

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