colCollapse,xgCMatrix-method {sparseMatrixStats} | R Documentation

## Extract one cell from each row (column) of a matrix-like object

### Description

Extract one cell from each row (column) of a matrix-like object.

### Usage

    ## S4 method for signature 'xgCMatrix'
    colCollapse(x, idxs, cols = NULL)

    ## S4 method for signature 'xgCMatrix'
    rowCollapse(x, idxs, rows = NULL)

### Arguments

`x` | An NxK matrix-like object.
`idxs` | An index `vector` with the position to extract. It is recycled to match the number of rows (column)
`cols` | A `vector` indicating the subset of rows (and/or columns) to operate over. If `NULL`, no subsetting is done.
`rows` | A `vector` indicating the subset of rows (and/or columns) to operate over. If `NULL`, no subsetting is done.

### Details

The S4 methods for `x` of type `matrix`, `array`, or `numeric` call `matrixStats::rowCollapse` / `matrixStats::colCollapse`.

### Value

Returns a `numeric` `vector` of length N (K).

### See Also

- `matrixStats::rowCollapse()` and `matrixStats::colCollapse()` which are used when the input is a `matrix` or `numeric` vector.

### Examples

    mat <- matrix(rnorm(15), nrow = 5, ncol = 3)
      mat[2, 1] <- NA
      mat[3, 3] <- Inf
      mat[4, 1] <- 0

      print(mat)

      rowCollapse(mat, idxs = 2)
      rowCollapse(mat, idxs = c(1,1,2,3,2))

      colCollapse (mat, idxs = 4)

[Package sparseMatrixStats version 1.2.1 Index]