Creating table with different row dimensions

Question

Let's say I got a table like this:

data <- c(1,2,3,6,5,6,9,"LC","LC","HC","HC","LC","HC","ALL")
attr(data,"dim") <- c(7,2)
data
     [,1] [,2] 
[1,] "1"  "LC" 
[2,] "2"  "LC" 
[3,] "3"  "HC" 
[4,] "6"  "HC" 
[5,] "5"  "LC" 
[6,] "6"  "HC" 
[7,] "9"  "ALL"

Now I want to manipulate the data so it looks like this:

     [,"LC"] [,"HC"] [,"ALL"] 
[1,] "1"     "3"     "9"
[2,] "2"     "6"
[3,] "5"     "6" 

Is there a way to do this in R or is it just impossible and should I try another way of getting access to my data?

Answer 1

You can get very close by using split. This returns a list with the values you wanted and you can then use lapply or any other list manipulation function:

split(data[, 1], data[, 2])

$ALL
[1] "9"

$HC
[1] "3" "6" "6"

$LC
[1] "1" "2" "5"

If you must have the output in matrix format, then I suggest you pad the short vectors with NA:

x <- split(data[, 1], data[, 2])
n <- max(sapply(x, length))

pad_with_na <- function(x, n, padding=NA){
  c(x, rep(padding, n-length(x)))
}

sapply(x, pad_with_na, n)

This results in:

     ALL HC  LC 
[1,] "9" "3" "1"
[2,] NA  "6" "2"
[3,] NA  "6" "5"