Extracting values with if and put them in a new column - r

Question

maybe this is a very simple question, but I cannot figure out what is wrong with my short code.
This is my (very simple) data frame:
structure(list(sample = structure(c(1L, 2L, 1L, 1L, 1L, 2L, 3L,
3L, 3L), .Label = c("a", "b", "c"), class = "factor"), value = c(0.1446689595,
0.9151456018, 0.880888083, 0.005522657, 0.7079621046, 0.4770259836,
0.6960717649, 0.5892328324, 0.1134234308), new = c("red", "red",
"red", "red", "red", "red", "red", "red", "red")), .Names = c("sample",
"value", "new"), row.names = c(NA, -9L), class = "data.frame")
what I would like to do is add a new column where the new values depend on the values of the first column. In other and simpler words:
if (df1$sample != "a") {
df1$new <- "green"
} else {
df1$new <- "red"
}
but R returns an error:
In if (df1$sample != "a") { :
the condition has length > 1 and only the first element will be used
I also tried with an elseif statement:
ifelse(df1$sample != "a", df1$new <- "green", df1$new <- "red")
but it this case the new column contains only "red" and no "green".
Am I missing something?
Thanks!

Answer 1

You could try
df1$new <- c('green', 'red')[(df1$sample=='a')+1L]
df1
# sample value new
#1 a 0.144668959 red
#2 b 0.915145602 green
#3 a 0.880888083 red
#4 a 0.005522657 red
#5 a 0.707962105 red
#6 b 0.477025984 green
#7 c 0.696071765 green
#8 c 0.589232832 green
#9 c 0.113423431 green

Answer 2

ifelse should work fine - you just need to assign it
df1$new1 <- ifelse(df1$sample != "a", df1$new1 <- "green", df1$new1 <- "red")
sample value new new1
1 a 0.144668959 red red
2 b 0.915145602 red green
3 a 0.880888083 red red
4 a 0.005522657 red red
5 a 0.707962105 red red
6 b 0.477025984 red green
7 c 0.696071765 red green
8 c 0.589232832 red green
9 c 0.113423431 red green
I would avoid using new as a variable name - it is the name of a function and this may cause issues.