apl {magic}

Replacements for APL functions take and drop

Description

Replacements for APL functions take and drop

Usage

apldrop(a, b, give.indices=FALSE)
apldrop(a, b) <- value
apltake(a, b, give.indices=FALSE)
apltake(a, b) <- value

Arguments

a

Array

b

Vector of number of indices to take/drop. Length of b should not exceed length(dim(a)); if it does, an error is returned

give.indices

Boolean, with default FALSE meaning to return the appropriate subset of array a, and TRUE meaning to return the list of the selected elements in each of the dimensions. Setting to TRUE is not really intended for the end-user, but is used in the code of apltake<-() and apldrop<-()

value

elements to replace

Details

apltake(a,b) returns an array of the same dimensionality as a. Along dimension i, if b[i]>0, the first b[i] elements are retained; if b[i]<0, the last b[i] elements are retained.

apldrop(a,b) returns an array of the same dimensionality as a. Along dimension i, if b[i]>0, the first b[i] elements are dropped if b[i]<0, the last b[i] elements are dropped.

These functions do not drop singleton dimensions. Use drop() if this is desired.

Author(s)

Robin K. S. Hankin

Examples

a <- magichypercube.4n(m=1)
apltake(a,c(2,3,2))
apldrop(a,c(1,1,2))

b <- matrix(1:30,5,6)
apldrop(b,c(1,-2)) <- -1

b <- matrix(1:110,10,11)
apltake(b,2) <- -1
apldrop(b,c(5,-7)) <- -2
b