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I couldn't find any reference to this in the FAQ, but is it possible to sort a dataframe by multiple columns? I've created some code, similar to the following: nspr.code <- sp.results$sp.code[order( sp.results$sp.code )] nspr.tpa <- sp.results$tpa[order( sp.results$sp.code )] nspr.code <- as.character( levels( nspr.code ) )[nspr.code] nspr.tpa <- as.numeric( levels( nspr.tpa