colMedians {DelayedMatrixStats} | R Documentation

## Calculates the median for each row (column) in a matrix

### Description

Calculates the median for each row (column) in a matrix.

### Usage

    colMedians(x, rows = NULL, cols = NULL, na.rm = FALSE, dim. = dim(x),
      ...)

    rowMedians(x, rows = NULL, cols = NULL, na.rm = FALSE, dim. = dim(x),
      ...)

    ## S4 method for signature 'DelayedMatrix'
    colMedians(x, rows = NULL, cols = NULL,
      na.rm = FALSE, dim. = dim(x), force_block_processing = FALSE, ...)

    ## S4 method for signature 'DelayedMatrix'
    rowMedians(x, rows = NULL, cols = NULL,
      na.rm = FALSE, dim. = dim(x), force_block_processing = FALSE, ...)

### Arguments

`x` | A NxK DelayedMatrix.
`rows` | A `vector` indicating subset of rows (and/or columns) to operate over. If `NULL`, no subsetting is done.
`cols` | A `vector` indicating subset of rows (and/or columns) to operate over. If `NULL`, no subsetting is done.
`na.rm` | If `TRUE`, `NA`s are excluded first, otherwise not.
`dim.` | An `integer` `vector` of length two specifying the dimension of `x`, also when not a `matrix`.
`...` | Additional arguments passed to specific methods.
`force_block_processing` | `FALSE` (the default) means that a seed-aware, optimised method is used (if available). This can be overridden to use the general block-processing strategy by setting this to `TRUE` (typically not advised). The block-processing strategy loads one or more (depending on `getOption("DelayedArray.block.size")`) columns (`colFoo()`) or rows (`rowFoo()`) into memory as an ordinary base::array.

### Details

The implementation of `rowMedians()` and `colMedians()` is optimized for both speed and memory. To avoid coercing to `double`s (and hence memory allocation), there is a special implementation for `integer` matrices. That is, if `x` is an `integer` `matrix`, then `rowMedians(as.double(x))` (`rowMedians(as.double(x))`) would require three times the memory of `rowMedians(x)` (`colMedians(x)`), but all this is avoided.

### Value

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

### See Also

See `rowWeightedMedians()` and `colWeightedMedians()` for weighted medians. For mean estimates, see `rowMeans2()` and `rowMeans()`.

### Examples

    # A DelayedMatrix with a 'Matrix' seed
    dm_Matrix <- DelayedArray(Matrix::Matrix(c(rep(1L, 5),
                                               as.integer((0:4) ^ 2),
                                               seq(-5L, -1L, 1L)),
                                             ncol = 3))

    colMedians(dm_Matrix)

    rowMedians(dm_Matrix)

[Package DelayedMatrixStats version 1.0.3 Index]