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

Value

Returns a numeric

vector of length N (K).

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.
useNames: If FALSE (default), no naming support is done. Else if TRUE, names attributes of result are set.

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

Henrik Bengtsson

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.