Skip to contents

Swap two double-precision vectors.

Source: R/bigalgebra.R
dswap.Rd

Exchange the elements of two double precision vectors in place. For I = 0 to N-1, swap DX(LX + I * INCX) with DY(LY + I * INCY) where LX and LY depend on the increment signs. When an optimized BLAS is available the implementation dispatches to DSWAP; otherwise a portable C loop performs the exchange.

Usage

dswap(N = NULL, X, INCX = 1L, Y, INCY = 1L)

Arguments

N

Number of elements in the input vectors. Defaults to the full length of X if NULL.

X

Double precision vector or matrix providing the first data block.

INCX

Storage spacing between elements of X.

Y

Double precision vector or matrix providing the second data block.

INCY

Storage spacing between elements of Y.

Value

Invisibly returns NULL; both X and Y are modified in place.

Details

When an optimized BLAS is available the implementation delegates to the Fortran DSWAP routine. Otherwise a portable C fallback performs the exchange directly while respecting the supplied vector increments.

See also

[dcopy()], [daxpy()] and [dscal()].

Examples

set.seed(4670)
X <- matrix(runif(6), 3, 2)
Y <- matrix(runif(6), 3, 2)
X_original <- X
Y_original <- Y
dswap(X = X, Y = Y)
all.equal(X, Y_original)
#> [1] "Mean relative difference: 0.274648"
all.equal(Y, X_original)
#> [1] "Mean relative difference: 0.2364376"