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...those ordered easily enough. What I'm struggling with is how to sort the categories (because I don't want them in a straight alphabetic order). library(stringr) d <- data.frame(instance = c("competition11","competition01","big_20","small_4","small_2","med_9")) id <- str_extract(d$instance, "\\d{1,}$") Any pointers would be gratefully received. Thanks, Alastair -- View this message in context: http://r.789695.n4.nabble.com/Sorting-a-Data-Frame-by-hybrid-string-number-key-tp3258283p3258283.html Sent from the R hel...