R: How to split a specific column based on symbol in R? [duplicate]

Question

Possible Duplicate:
Replacing ^ and | sybmbols in a matrix

In previous message (Replacing ^ and | sybmbols in a matrix), the way to remove a symbol in a list wass discussed.

Here I want to replace only one column (column Drug) of a matrix. For example:

Patient Hospital Drug Response
111     AAA      B+A  Good
222     CCC      B    Good
333     DDD      A+C  Bad+relapse

To the following formats.

Patient Hospital Drug1 Drug2 Response
111     AAA      B     A     Good
222     CCC      B     NA    Good
333     DDD      A     C     Bad+relapse

What is the way to do so with R.

Answer 1

Like this:

df <- data.frame(drug1 = c("B+A", "B", "A+C"))
df
df$drug2 <- lapply(strsplit(as.character(df$drug1), "\\+"), "[", 2)
df$drug1 <- lapply(strsplit(as.character(df$drug1), "\\+"), "[", 1)
df

resulting

> df
  drug1 drug2
1     B     A
2     B    NA
3     A     C
>