Add a suffix and prefix to some column names in R

Question

I have a column name Food_Q_74 in a loop that becomes Food_Q_75 Food_Q_76 etc

I need to make it look like Q_74_A1, Q_75_A1 etc

I need to delete Food_ at the beginning and add _A1 at the end. So I am NOT adding a prefix as suggested. I am not only pasting at the end.

Any real help would be appreciated.

gsub('^Food_',' ',colnames(df$columns)) this deletes the Food_ but I can not figure out the code to add a suffix. Also, when I run that in R it does not change the column name. When I run it in the console it shows the deletion. ???

I thought ^ was for the start and $ for the end so I tried gsub('^Food_$ '',_A1',df$columns) but this is wrong.

Answer 1

You could simply pasting the interim result together with "_A1":

without_food <- gsub('^Food_',' ',colnames(df$columns))

with_a1 <- paste0(without_food, "_A1")

An alternative to paste0 would be str_c from the stringr package.

Answer 2

To add something to a string (character), use the paste0-function.

namesWithoutFood <- gsub('^Food_',' ',colnames(df$columns))
paste0(namesWithoutFood,"_A1")

Answer 3

You can do this all within gsub, without using paste:

gsub("^Food_(.*)$", "\\1_A1", colnames(df$columns))

The (.*)$ here means "Capture all characters after 'Food_' until the end of the string". The \\1_A in the replacement means "Use the captured group here and stick '_A' on the end."

Answer 4

had

colnames(finalmydat[,138:152])

but needed

colnames(finalmydat)[138:152]