R: Calculates the product for each row (column) in a matrix

product {matrixStats} | R Documentation

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

### Description

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

### Usage

    product(x, idxs = NULL, na.rm = FALSE, ...)

    rowProds(x, rows = NULL, cols = NULL, na.rm = FALSE,
      method = c("direct", "expSumLog"), ...)

    colProds(x, rows = NULL, cols = NULL, na.rm = FALSE,
      method = c("direct", "expSumLog"), ...)

### Arguments

`x` | An NxK `matrix` or, if `dim.` is specified, an N * K `vector`.
`idxs` | A `vector` indicating subset of elements to operate over. If `NULL`, no subsetting is done.
`na.rm` | If `TRUE`, missing values are excluded.
`...` | Not used.
`rows` | A `vector` indicating subset of rows to operate over. If `NULL`, no subsetting is done.
`cols` | A `vector` indicating subset of columns to operate over. If `NULL`, no subsetting is done.
`method` | A `character` string specifying how each product is calculated.

### Details

If `method = "expSumLog"`, then then `product`() function is used, which calculates the product via the logarithmic transform (treating negative values specially). This improves the precision and lowers the risk for numeric overflow. If `method = "direct"`, the direct product is calculated via the `prod`() function.

### Value

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

### Missing values

Note, if `method = "expSumLog"`, `na.rm = FALSE`, and `x` contains missing values (`NA` or `NaN`), then the calculated value is also missing value. Note that it depends on platform whether `NaN` or `NA` is returned when an `NaN` exists, cf. `is.nan`().

### Author(s)

Henrik Bengtsson

[Package matrixStats version 0.59.0 Index]