expand: Expand a matrix to larger dimensions, filling in new entries

In futile.matrix: Random Matrix Generation and Manipulation

Description

Provides a convenient mechanism for expanding the dimensions of a matrix with a specified default value. This is particularly useful if the matrix needs to match dimensions with another matrix. Expand can take either another matrix or a set of dimnames to grow the matrix. In either case, the expanded matrix will have dimensions that match the explicitly or implicitly specified dimnames.

Usage

expand(m, target, default = 0)

Arguments

m	A matrix to expand
target	A list containing the dimnames or a matrix that contains dimnames
default	The default value to use for the new entries

Details

To properly expand m to target, the rownames and colnames of m must be a strict subset of target's rownames and colnames. If this requirement is not satisfied, the behavior is currently undefined (although most likely an error will result). In the future, the behavior might be configurable to drop those rows/columns that are not in target's rownames/colnames.

In general, expand tries to err on the side of accomodation, although the implementation is incomplete. If target is a list, then the format is the same as when constructing a matrix and passing dimnames as an argument. Currently, only a list or a matrix are supported. If a list, target[[0]] represent the row names and target[[1]] are the column names. This could be relaxed in the future to any object that has a rownames and colnames.

Note that a current limitation/feature in expand is that it orders the resulting matrix by rows and columns. More precise control needs to be provided here, with the default being the ordering of the rows and columns conforming to target.

TODO: Consistency check to ensure all rownames/colnames of m are a subset of target

Value

The expanded matrix with rows and columns corresponding to the target dimnames

Examples

rows.m <- c('row.1', 'row.2', 'row.3')
cols.m <- c('col.1', 'col.2')
rows.n <- c(rows.m, 'row.4')
cols.n <- c(cols.m, 'col.3')
m <- matrix(c(1,4,7,2,5,8), ncol=2, dimnames=list(rows.m,cols.m))
n <- matrix(c(1,4,7,10,2,5,8,11,3,6,9,12), ncol=3,
  dimnames=list(rows.n,cols.n))
expand(m, n)

Example output

      col.1 col.2 col.3
row.1     1     2     0
row.2     4     5     0
row.3     7     8     0
row.4     0     0     0

futile.matrix documentation built on May 2, 2019, 4:22 a.m.