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"]