Reduce row in a table following a criteria with R

Question

I have a table like this: df <- c("A", "B", "A", "C", "A", "D") df <- as.data.frame(df) df$number <- c("11", "12", "13", "11", "12", "14")

and I want to reduce number of row aggregating like this: df_final <- c("A", "B", "C", "D") df_final <- as.data.frame(df_final) df_final$number <- c("11; 13; 12", "12", "11", "14")

how can I do it?