R : remove NULL in each column while keeping order in the column

January 27, 2023

I have a data frame with NULLs or Nos in R:
Example:

people1 <- c("Variety 1", "Variety 2", "Variety 3", "Variety 4", "Variety 5")
people2 <- c("Variety 4", "Variety 3", "Variety 2", "Variety 1", "NULL")
people3 <- c("Variety 3", "Variety 2", "NULL", "Variety 4", "Variety 1")
df2 <- data.frame(people1, people2, people3)

For each column, if there is a NULL or NA, I want them removed and the next item moved up to replace.
So that the columns may end with NULLs but not have them in the middle.

Can you help?
Thanks!

>Solution :

Note that the question was changed after I answered it and the answer to the original question is at the bottom under Old. The answer to the new question is:

replace(df2, TRUE, lapply(df2, function(x) c(x[x != "NULL"], x[x == "NULL"])))

giving:

    people1   people2   people3
1 Variety 1 Variety 4 Variety 3
2 Variety 2 Variety 3 Variety 2
3 Variety 3 Variety 2 Variety 4
4 Variety 4 Variety 1 Variety 1
5 Variety 5      NULL      NULL

Old

Convert the "NULL" values to NA and use na.locf (last occurrence carried forward). It will also work if there are multiple consecutive "NULL" values.

library(zoo)

m <- as.matrix(df2)
replace(df2, TRUE, na.locf(ifelse(m == "NULL", NA, m)))

giving:

    people1   people2   people3
1 Variety 1 Variety 4 Variety 3
2 Variety 2 Variety 3 Variety 2
3 Variety 3 Variety 2 Variety 2
4 Variety 4 Variety 1 Variety 4
5 Variety 5 Variety 1 Variety 1