[R] ungrouping grouped data

[Douglas Bates]

Michael Friendly <friendly at yorku.ca> writes:

> I'm sure this is probably simple, but I can't find an answer...
> I have a data frame (Galton's data on heights of parents and
> children), in grouped form,
> 
> 
> parent child frequency
> 73.5 72.2 1
> 73.5 73.2 3
> 72.5 68.2 1
> 72.5 69.2 2
> 72.5 70.2 1
> 72.5 71.2 2
> 72.5 72.2 7
> 72.5 73.2 2
> 72.5 74.2 4
> 71.5 65.2 1
> 71.5 66.2 3
> 71.5 67.2 4
> 71.5 68.2 3
> 71.5 69.2 5
> 71.5 70.2 10
> ...
> 
> and need the ungrouped equivalent, where each input observation
> appears the number of times represented by its frequency.

If df is the name of the data frame you want

df[rep(1:nrow(df), df$frequency), 1:2]