How to pad a matrix with named rows and columns?

Question

Suppose you have a matrix (X) and a second matrix (src) such that rownames of X are a subset of the rownames of src and the colnames of X are a subset of the colnames of src. What is the best way to create a matrix with the rows and columns of src, the data of X, and with missing data filled in with some default value (such as zero or NA)?

Below is my attempt, but I feel there must be a standard way of doing this in R.

# Assume row and columns are named
PadColumns <- function(x, src, fill = NA) {
  # pad columns with default values
  result <- matrix(fill, nrow = nrow(x), ncol = ncol(src))
  colnames(result) <- colnames(src)
  rownames(result) <- rownames(x)
  result[,match(colnames(x), colnames(src))] <- x
  result
}

PadRows <- function(x, src, fill = NA) {
  # pad rows with default values
  result <- matrix(fill, nrow = nrow(src), ncol = ncol(x))
  colnames(result) <- colnames(x)
  rownames(result) <- rownames(src)
  result[match(rownames(x), rownames(src)),] <- x
  result
}

PadRowsColumns <- function(x, src, fill = NA) {
  PadColumns(PadRows(x, src, fill = fill), src, fill = fill)
}

For example, given

X <- matrix(1:6, nrow = 2, dimnames = list(letters[2 * 1:2], LETTERS[2 * 1:3]))
src <- matrix(0, nrow = 4, ncol = 6, dimnames = list(letters[1:4], LETTERS[1:6]))

then we should get this:

> X
  B D F
b 1 3 5
d 2 4 6
> PadRowsColumns(X, src)
   A  B  C  D  E  F
a NA NA NA NA NA NA
b NA  1 NA  3 NA  5
c NA NA NA NA NA NA
d NA  2 NA  4 NA  6

Kota Mori Kota Mori · Accepted Answer · 2016-08-30T17:43:31

You can subset matrices by row and column names.

src <- matrix(1, nrow = 3, ncol = 4, 
              dimnames= list(c("a", "b", "c"), c("A", "B", "C", "D")))
X <- matrix(1:6, nrow = 2, ncol = 3,
            dimnames = list(c("b", "c"), c("A", "C", "D")))
Y <- src
Y[] <- NA
Y[rownames(X), colnames(X)] <- X

How to pad a matrix with named rows and columns?

1 Answers