r - Add empty columns to a dataframe with specified names from a vector

Question

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?

Answer 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