I want to sort elements by frequency . For example let x = ["a", "d", "d", "c", "c", "c", "f", "b", "b" ,"b", "b"] I want to have output sorted as x = ["b", "b" ,"b", "b","c", "c", "c, "d", "d", "a", "f"] where we have 4 b , 3 c , 2d , 1a and 1f.

You can use StatsBase: using StatsBase function to_sort_x(x) counts = countmap(x) sorted_x = sort(x, by=x -> counts[x], rev=true) return sorted_x end sorted_x = to_sort_x(x) If you’re using DataFrames, you can also do this using DataFrames x = ["a", "d", "d", "c", "c", "c", "f", …

Also using StatsBase, but with rle and its inverse instead of countmap: function sort_by_count(x) v, l = rle(x) idxs = sortperm(l; rev=true) return @views inverse_rle(v[idxs], l[idxs]) end Some minimal benchmarking suggests that this performs a few times faster than the countmap based …

@digital_carver Nice! I think you need to sort the incoming x otherwise the run length encoding won’t aggregate non-adjacent values.

Sort elements by frequency in julia

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rafael.guerra September 5, 2023, 9:21pm 5

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Sort elements by frequency in julia

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