Try also:

df1 <- data.frame(a = LETTERS[1:2], b = LETTERS[3:4], c = 1:2)
df1$a <- as.character(df1$a) #if is factor
df1$b <- as.character(df1$b) #if is factor
df1[df1$c == 2, ] <- c(subset(df1, c == 2, select = c("b", "a")), 2)

On Thu, Apr 17, 2008 at 11:52 AM, Michael Kubovy <kubovy@virginia.edu>
wrote:

> df1 <- data.frame(a = LETTERS[1:2], b = LETTERS[3:4], c = 1:2)
>
> I am looking for an idiom that swaps the elements of df$a and df$b
> when (e.g.) df$c == 2, resulting in
>
> df2 <- data.frame(a = LETTERS[c(1, 4)], b = LETTERS[c(3, 2)], c = 1:2)
> _____________________________
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>
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-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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