In a large dataframe ("myfile") with four columns I have to add a fifth column with values conditionally based on the first four columns.
Prefer answers with dplyr
and mutate
, mainly because of its speed in large datasets.
My dataframe looks like this:
V1 V2 V3 V4
1 1 2 3 5
2 2 4 4 1
3 1 4 1 1
4 4 5 1 3
5 5 5 5 4
...
The values of the fifth column (V5) are based on some conditional rules:
if (V1==1 & V2!=4) {
V5 <- 1
} else if (V2==4 & V3!=1) {
V5 <- 2
} else {
V5 <- 0
}
Now I want to use the mutate
function to use these rules on all rows (to avoid slow loops). Something like this (and yes, I know it doesn't work this way!):
myfile <- mutate(myfile, if (V1==1 & V2!=4){V5 = 1}
else if (V2==4 & V3!=1){V5 = 2}
else {V5 = 0})
This should be the result:
V1 V2 V3 V4 V5
1 1 2 3 5 1
2 2 4 4 1 2
3 1 4 1 1 0
4 4 5 1 3 0
5 5 5 5 4 0
How to do this in dplyr
?
NA
, (NaN, +Inf, -Inf
)? – smcidplyr
, then I would better usedata.table
. – Valentin