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Transform between Linear Index and Matrix Indices

idx_trafo.Rd

These functions are as in MATLAB. ind2sub() transforms a linear index to a row and column index for a matrix of given size. sub2ind() transforms a matrix index, (row, col) to a a linear index (in terms of columns).

Usage

ind2sub(dim, ind)

sub2ind(dim, row, col)

Arguments

dim

Integer vector of size 2. Matrix dimensions.

ind

Integer. Linear index.

row

Integer. Row index.

col

Integer. Column index.

Value

ind2sub() returns for given linear index, a matrix index (row, col).

sub2ind() returns for a given matrix index (row, col), a linear index (column-major).

Examples

A = matrix(1:(3*4), 3, 4)
A
#>      [,1] [,2] [,3] [,4]
#> [1,]    1    4    7   10
#> [2,]    2    5    8   11
#> [3,]    3    6    9   12

ind2sub(c(3,4), 7)
#> [1] 1 3
sub2ind(c(3,4), 2, 3)
#> [1] 8