Add empty columns to a dataframe with specified names from a vector
I have a dataframe, df, with a a number of columns of data already. I have a vector, namevector, full of strings. I need empty columns added to df with the names of the columns from namevector.
I am trying to add columns with this for loop, iterating over each string in namevector.
for (i in length(namevector)) {
df[, i] <- NA
}
but am left with this error:
Error in
[<-.data.frame(*tmp*, , i, value = NA) : new columns would leave holes after existing columns
Alternatively, I have thought of creating an empty dataframe with the correct names, then cbind-ing the two dataframes together but am not sure how to go about coding this.
How would I go about resolving this?
Solution 1:
The problem with your code is in the line:
for(i in length(namevector))
You need to ask yourself: what is length(namevector)? It's one number. So essentially you're saying:
for(i in 11)
df[,i] <- NA
Or more simply:
df[,11] <- NA
That's why you're getting an error. What you want is:
for(i in namevector)
df[,i] <- NA
Or more simply:
df[,namevector] <- NA
Solution 2:
set.seed(1)
example <- data.frame(col1 = rnorm(10, 0, 1), col2 = rnorm(10, 2, 3))
namevector <- c("col3", "col4")
example[ , namevector] <- NA
example
# col1 col2 col3 col4
# 1 -0.6264538 6.5353435 NA NA
# 2 0.1836433 3.1695297 NA NA
# 3 -0.8356286 0.1362783 NA NA
# 4 1.5952808 -4.6440997 NA NA
# 5 0.3295078 5.3747928 NA NA
# 6 -0.8204684 1.8651992 NA NA
# 7 0.4874291 1.9514292 NA NA
# 8 0.7383247 4.8315086 NA NA
# 9 0.5757814 4.4636636 NA NA
# 10 -0.3053884 3.7817040 NA NA
Solution 3:
The below works for me
dataframe[,"newName"] <- NA
Make sure to add "" for new name string.