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

Description Usage Arguments Details Value Author(s) See Also Examples

Description

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

Usage

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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, NAs 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 \link[DelayedArray]{getAutoBlockSize}()) 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 doubles (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).

Author(s)

Peter Hickey

See Also

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

Examples

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# 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)

DelayedMatrixStats documentation built on July 8, 2020, 9:22 p.m.