Às 21:05 de 11/06/2023, javad bayat escreveu:
Dear R users;
I am trying to fill a column based on a specific value in another column of
a dataframe, but it seems there is a problem with the codes!
The "Layer" and the "LU" are two different columns of the dataframe.
How can I fix this?
Sincerely
for (i in 1:nrow(data2$Layer)){
if (data2$Layer == "Level 12") {
data2$LU == "Park"
}
}
Hello,
There are two bugs in your code,
1) the index i is not used in the loop
2) the assignment operator is `<-`, not `==`
Here is the loop corrected.
for (i in 1:nrow(data2$Layer)){
if (data2$Layer[i] == "Level 12") {
data2$LU[i] <- "Park"
}
}
But R is a vectorized language, the following two ways are the idiomac
ways of doing what you want to do.
i <- data2$Layer == "Level 12"
data2$LU[i] <- "Park"
# equivalent one-liner
data2$LU[data2$Layer == "Level 12"] <- "Park"
If there are NA's in data2$Layer it's probably safer to use ?which() in
the logical index, to have a numeric one.
i <- which(data2$Layer == "Level 12")
data2$LU[i] <- "Park"
# equivalent one-liner
data2$LU[which(data2$Layer == "Level 12")] <- "Park"
Hope this helps,
Rui Barradas
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