Check if a column exists and if not add it-CodePudding

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.

CodePudding user response：

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