Expand a frequency table to case form

Converts a frequency table, given either as a table object or a data frame in frequency form to a data frame representing individual observations in the table.

Usage

expand.dft(x, var.names = NULL, freq = "Freq", ...)

expand.table(x, var.names = NULL, freq = "Freq", ...)

Arguments

x: A table object, or a data frame in frequency form containing factors and one numeric variable representing the cell frequency for that combination of factors.
var.names: A list of variable names for the factors, if you wish to override those already in the table
freq: The name of the frequency variable in the table
...: Other arguments passed down to type.convert. In particular, pay attention to na.strings (default: na.strings=NA if there are missing cells) and as.is (default: as.is=FALSE, converting character vectors to factors).

Details

expand.table is a synonym for expand.dft.

Value

A data frame containing the factors in the table and as many observations as are represented by the total of the freq variable.

References

Originally posted on R-Help, Jan 20, 2009, http://tolstoy.newcastle.edu.au/R/e6/help/09/01/1873.html

Friendly, M. and Meyer, D. (2016). Discrete Data Analysis with R: Visualization and Modeling Techniques for Categorical and Count Data. Boca Raton, FL: Chapman & Hall/CRC. http://ddar.datavis.ca.

Author

Mark Schwarz

Examples

library(vcd)
art <- xtabs(~Treatment + Improved, data = Arthritis)
art
#>          Improved
#> Treatment None Some Marked
#>   Placebo   29    7      7
#>   Treated   13    7     21
artdf <- expand.dft(art)
str(artdf)
#> 'data.frame':	84 obs. of  2 variables:
#>  $ Treatment: chr  "Placebo" "Placebo" "Placebo" "Placebo" ...
#>  $ Improved : chr  "None" "None" "None" "None" ...

# 1D case
(tab <- table(sample(head(letters), 20, replace=TRUE)))
#> 
#> a b c d e f 
#> 1 2 3 2 9 3 
expand.table(tab, var.names="letter")
#>    letter
#> 1       a
#> 2       b
#> 3       b
#> 4       c
#> 5       c
#> 6       c
#> 7       d
#> 8       d
#> 9       e
#> 10      e
#> 11      e
#> 12      e
#> 13      e
#> 14      e
#> 15      e
#> 16      e
#> 17      e
#> 18      f
#> 19      f
#> 20      f