Commands to transform data.frame in R

Question

I'm struggling with coming up with the correct process to transform some data I'm doing analysis on without resorting to a scripting language.

The data takes a format similar to the following

data.frame(Group=LETTERS[1:3],Total=c(100,120,130),Modified=c(12,15,32))

  Group Total Modified
1     A   100       12
2     B   120       15
3     C   130       32

I'd like the resulting data frame to look like

    +-------+----------+
    | Group | Modified |
    +-------+----------+
    | A     | Y        |
    | A     | Y        |
    | A     | Y        |
    | .     | .        |
    | .     | .        |
    | .     | .        |
    | A     | N        |
    | A     | N        |
    | B     | Y        |
    | B     | Y        |
    | .     | .        |
    | .     | .        |
    | .     | .        |
    | B     | N        |
    +-------+----------+

There should be 12 rows with Group A and Modified = Y and 88 rows with Group A and Modified = N. Same goes for B, C, etc.

In most cases there are additional columns that will need to be repeated on each row along with the Group info.

Answer 1

You can use rep with the appropriate times argument.

A data.table solution for coding elegance

library(data.table)
# your data is in the data.frame DF
DF <- data.table(DF)
levels <- c('Y', 'N')
DF[,list(Modified = rep(levels,c(Modified,Total-Modified))),by = Group]