Splitting a numeric column for a dataframe

Question

I have a dataframe df as shown below

  name  position            
1 HLA   1:1-15            
2 HLA   1:2-16 
3 HLA   1:3-17         

I would like to split the position column into two more columns based on the ":" character such that i get

name    seq    position            
1 HLA   1       1-15            
2 HLA   1       2-16 
3 HLA   1       3-17 

So i thought this would do the trick,

df <- transform(df,pos = as.character(position)) 

df_split<- strsplit(df$pos, split=":")

#found this hack from an old mailing list post
df <- transform(df, seq_name= sapply(df_split, "[[", 1),pos2= sapply(df_split, "[[", 2))

however I get an error

Error in strsplit(df$pos, split = ":") : non-character argument

What could be wrong? How do you achieve this in R. I have simplified my case here, actuality the dataframe runs to over a hundred thousand rows.

Answer 1

df_split<- strsplit(as.character(df$position), split=":")
df <- transform(df, seq_name= sapply(df_split, "[[", 1),pos2= sapply(df_split, "[[", 2))
> 
> df
  name position    pos seq_name pos2
1  HLA   1:1-15 1:1-15        1 1-15
2  HLA   1:2-16 1:2-16        1 2-16
3  HLA   1:3-17 1:3-17        1 3-17

Answer 2

Here is a one line method using tidyr.separate():

library(tidyr)
df <- separate(df, position, into = c("seq","position"), sep = ":", extra = "merge")

Answer 3

The "trick" is to use do.call.

> a <- data.frame(x = c("1:1-15", "1:2-16", "1:3-17"))
> a
       x
1 1:1-15
2 1:2-16
3 1:3-17
> a$x <- as.character(a$x)
> a.split <- strsplit(a$x, split = ":")
> tmp <-do.call(rbind, a.split)
> data.frame(a, tmp)
       x X1   X2
1 1:1-15  1 1-15
2 1:2-16  1 2-16
3 1:3-17  1 3-17