D2A: data.frame.to.array package:mvbutils

In mvbutils: General utilities, workspace organization, code and doc editing, live package maintenance, etc

data.frame.to.array package:mvbutils

Description

D2A makes an array out of one column in a dataframe, with (by default) the remaining columns forming the array dimensions, in order. Its (almost) inverse is A2D.

You can choose which columns to use for the dimensions, and in which order, via the dim.cols argument. However, it often easier to subset the array by columns in the call, eg D2A( x[ cq( Year, Len, Count), data.col="Count"). Each unique value in an index column gets a "row" in the array. Combinations of indices that don't appear as rows in the input will become missing.value in the output. If a row has missing values in any index column, it is ignored.

Duplicated index rows in the data.frame are not advisable, and trigger a warning; I think the last value will be used, but I'm not sure.

Note

D2A and (something similar to) A2D used to be in my semi-secret handy2 package under slightly different names, but they are useful enough that I've moved them to mvbutils in 2025.

You can of course do vaguely similar things with base-R and perhaps with countless other packages too, but why not just use this? I do!

Usage

D2A(
  df,
  data.col,
  dim.cols = names(df) %except% data.col,
  missing.value = NA)

Arguments

df	data.frame
dim.cols	character vector saying which columns (in order) to use for array dimensions. Default is everything except data.col
data.col	string saying which column should form the contents of the output
missing.value	what to put into the output for index-combinations that don't occur in the input.

Value

Array with length( dim.cols) dimensions, and appropriate dimnames.

D2a

Dataframe to array

See Also

A2D

Examples

grubbb <- expand.grid( xx=1:4, yy=2:3) # data.frame
grubbb$z <- with( grubbb, xx+10*yy)
D2A( grubbb, 'z')
# Let's remove some values, and change the order of array dims...
minigrubbb <- grubbb[ c( 1, 3, 4, 7),]
D2A( minigrubbb, 'z', dim.cols=cq( yy, xx))
# Don't have to use all columns
D2A( minigrubbb, 'z', dim.cols='xx')

mvbutils documentation built on May 25, 2026, 5:09 p.m.