Question

Hi I have a table with comma delimited columns and I need to convert the comma delimited values to new rows. for exmaple the given table is

Name     Start      End 
A        1,2,3    4,5,6
B          1,2      4,5
C      1,2,3,4  6,7,8,9   

I need to convert it like

Name Start End
   A     1   4
   A     2   5  
   A     3   6
   B     1   4
   B     2   5 
   C     1   6
   C     2   7
   C     3   8   
   C     4   9

I can do that using VB script but I need to solve it using R
Can anyone solve this?

Answer 1

Here’s an approach that should work for you. I’m assuming that your three input vectors are in different objects. We are going to create a list of those inputs and write a function that process each object and returns them in the form of a data.frame with plyr.

The things to take note of here are the splitting of the character vector into it’s component parts, then using as.numeric to convert the numbers from the character form when they were split. Since R fills matrices by column, we define a 2 column matrix and let R fill the values for us. We then retrieve the Name column and put it all together in a data.frame. plyr is nice enough to process the list and convert it into a data.frame for us automatically.

library(plyr)

a <- paste("A",1, 2,3,4,5,6, sep = ",", collapse = "")
b <- paste("B",1, 2,4,5, sep = ",", collapse = "")
c <- paste("C",1, 2,3,4,6,7,8,9, sep = ",", collapse = "")

input <- list(a,b,c)

splitter <- function(x) {
    x <- unlist(strsplit(x, ","))
    out <- data.frame(x[1], matrix(as.numeric(x[-1]), ncol = 2))
    colnames(out) <- c("Name", "Start", "End")
    return(out)
}


ldply(input, splitter)

And the output:

> ldply(input, splitter)
 Name Start End
1    A     1   4
2    A     2   5
3    A     3   6
4    B     1   4
5    B     2   5
6    C     1   6
7    C     2   7
8    C     3   8
9    C     4   9