Using a 2-column mapping dataframe in R to change values in main dataframe

Question

Apologies if this is a duplicate question, I have a feeling it has been asked, but I will provide a good example to help with understanding this. First the demo dataframes:

Answer 1

Another way would be to use your map_df as a look-up table.

rownames(map_df) = map_df$name
main_df$P1 = map_df[main_df$P1, "id"]
main_df$P2 = map_df[main_df$P2, "id"]

Answer 2

We can use match. Loop over the columns with lapply, match with 'name' column of 'map_df' and use the numeric index to change the values to the corresponding 'id' in 'map_df', assign the output to 'main_df'

main_df[] <- lapply(main_df, function(x) map_df$id[match(x, map_df$name)])

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Or convert it to a matrix and match it

main_df[] <- setNames(map_df$id, map_df$name)[as.matrix(main_df)]