bigmemory (version 4.5.36)

morder: Ordering and Permuting functions for big.matrix'' and matrix'' objects

Description

The morder function returns a permutation of row indices which can be used to rearrange an object according to the values in the specified columns (a multi-column ordering). The mpermute function actually reorders the rows of a big.matrix or matrix based on an order vector or a desired ordering on a set of columns.

Usage

morder(x, cols, na.last = TRUE, decreasing = FALSE)
morderCols(x, rows, na.last = TRUE, decreasing = FALSE)
mpermute(x, order = NULL, cols = NULL, allow.duplicates = FALSE, ...)
mpermuteCols(x, order = NULL, rows = NULL, allow.duplicates = FALSE, ...)

Arguments

x

A big.matrix or matrix object with numeric values.

cols

The columns of x to get the ordering for or reorder on

na.last

for controlling the treatment of NAs. If TRUE, missing values in the data are put last; if FALSE, they are put first; if NA, they are removed.

decreasing

logical. Should the sort order be increasing or decreasing?

rows

The rows of x to get the ordering for or reorder on

order

A vector specifying the reordering of rows, i.e. the result of a call to order or morder.

allow.duplicates

ff TRUE, allows a row to be duplicated in the resulting big.matrix or matrix (i.e. in this case, order would not need to be a permutation of 1:nrow(x)).

...

optional parameters to pass to morder when cols is specified instead of just using order.

Value

morder returns an ordering vector. mpermute returns nothing but does change the contents of x. This type of a side-effect is generally frowned upon in R, but we ``break'' the rules here to avoid memory overhead and improve performance.

Details

The morder function behaves similar to order, returning a permutation of 1:nrow(x) which rearranges objects according to the values in the specified columns. However, morder takes a big.matrix or an R matrix (with numeric type) and a set of columns (cols) with which to determine the ordering; morder does not incur the same memory overhead required by order, and runs more quickly.

The mpermute function changes the row ordering of a big.matrix or matrix based on a vector order or an ordering based on a set of columns specified by cols. It should be noted that this function has side-effects, that is x is changed when this function is called.

See Also

order

Examples

# NOT RUN {
m = matrix(as.double(as.matrix(iris)), nrow=nrow(iris))
morder(m, 1)
order(m[,1])

m[order(m[,1]), 2]
mpermute(m, cols=1)
m[,2]
# }