sparse.extract.index: Sparse indexing of matrices

Description Usage Arguments Details Value Examples

View source: R/sparse.extract.index.R

Description

Computes a matrix index that extracts individual (i, j) elements. This differ from the standard extraction where all columns in rows i and all rows in columns j are extracted.

Usage

1
2
sparse.extract.index(i, j, nrow, ncol, byrow = FALSE, na.rm = FALSE,
  quiet = TRUE)

Arguments

i, j

the indices of the elements to extract. i and j must have the same length.

nrow, ncol

the number of rows and colums of the index. currently, ncol is ignored with byrow = FALSE, nrow is ignored with byrow = TRUE

byrow

only FALSE is supported for now

na.rm

remove elements where i or j are NA

quiet

if FALSE, prints a message before removing the missing values. If TRUE, missing values are silently removed.

Details

Note that this is likely to NOT work on data frames.

Value

the vector index for the matrix. Typically one would want to use this index to extract from a matrix, and a vector will be returned, regardless of the status of drop.

Examples

1
2
3
4
5
m <- matrix(1:25, 5, 5)
m[1:5, 1:5] # Returns the whole matrix
m[sparse.extract.index(1:5, 1:5, nrow = 5)] # Returns the diagonal only
m[c(1, 3, 5), c(2, 4, 4)]
m[sparse.extract.index(c(1, 3, 5), c(2, 4, 4), nrow = 5)]

xrobin/xavamess documentation built on May 13, 2018, 12:15 p.m.