USING: arrays grouping kernel locals math.functions sequences ;

IN: math.statistics

:: quantile-abcd ( seq qs a b c d -- quantile )
seq qs a b c d quantile-indices :> indices indices
[ [ floor ] [ ceiling ] bi 2array ] map
concat :> index-pairs seq index-pairs kth-smallests 2 group
indices [ [ first2 ] dip c d qabcd ] 2map ;