Check if a column exists and if not add it

Question

I have a series of dataframes that are noncumulative. During the cleaning process I want to loop through the dataframe and check if certain columns exists and if they aren't present create them. I can't for the life of me figure out a method to do this. I am not package shy and prefer them to base.

Any direction is much appreciated.

This should provide you the answer: https://stackoverflow.com/questions/10276092/to-find-whether-a-column-exists-in-data-frame-or-not — carl, Jun 30 '22 at 15:01

score 1 · Accepted Answer · answered Jun 30 '22 at 15:09

You can use this dummy data df and colToAdd columns to check if not exists to add

df <- data.frame(A = rnorm(5) , B = rnorm(5) , C = rnorm(5))

colToAdd <- c("B" , "D")

then apply the check if the column exists NULL produced else add your column e.g. rnorm(5)

add <- sapply(colToAdd , \(x) if(!(x %in% colnames(df))) rnorm(5))

data.frame(do.call(cbind , c(df , add)))

output

           A          B          C          D
1  1.5681665 -0.1767517  0.6658019 -0.8477818
2 -0.5814281 -1.0720196  0.5343765 -0.8259426
3 -0.5649507 -1.1552189 -0.8525945  1.0447395
4  1.2024881 -0.6584889 -0.1551638  0.5726059
5  0.7927576  0.5340098 -0.5139548 -0.7805733

Seamless, many thanks to you my friend. – a nony mouse Jun 30 '22 at 15:58 — a nony mouse, Jun 30 '22 at 15:58

Check if a column exists and if not add it

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