diff --git a/extra/math/statistics/statistics-docs.factor b/extra/math/statistics/statistics-docs.factor index 695834b554..7a7eb70dd2 100644 --- a/extra/math/statistics/statistics-docs.factor +++ b/extra/math/statistics/statistics-docs.factor @@ -3,13 +3,14 @@ IN: math.statistics HELP: geometric-mean { $values { "seq" "a sequence of numbers" } { "n" "a non-negative real number"} } -{ $description "Computes the geometric mean of all elements in " { $snippet "seq" } ". The geometric mean measures the central tendency of a data set that minimizes the effects of extreme values." } +{ $description "Computes the geometric mean of all elements in " { $snippet "seq" } ". The geometric mean measures the central tendency of a data set that minimizes the effects of extreme values." } { $examples { $example "USING: math.statistics prettyprint ;" "{ 1 2 3 } geometric-mean ." "1.81712059283214" } } { $errors "Throws a " { $link signal-error. } " (square-root of 0) if the sequence is empty." } ; HELP: harmonic-mean { $values { "seq" "a sequence of numbers" } { "n" "a non-negative real number"} } -{ $description "Computes the harmonic mean of the elements in " { $snippet "seq" } ". The harmonic mean is appropriate when the average of rates is desired." } +{ $description "Computes the harmonic mean of the elements in " { $snippet "seq" } ". The harmonic mean is appropriate when the average of rates is desired." } +{ $notes "Positive reals only." } { $examples { $example "USING: math.statistics prettyprint ;" "{ 1 2 3 } harmonic-mean ." "6/11" } } { $errors "Throws a " { $link signal-error. } " (divide by zero) if the sequence is empty." } ; @@ -36,21 +37,21 @@ HELP: range HELP: std { $values { "seq" "a sequence of numbers" } { "x" "a non-negative real number"} } -{ $description "Computes the standard deviation of " { $snippet "seq" } " by squaring the variance of the sequence. It measures how widely spread the values in a sequence are about the mean." } +{ $description "Computes the standard deviation of " { $snippet "seq" } ", which is the square root of the variance. It measures how widely spread the values in a sequence are about the mean." } { $examples { $example "USING: math.statistics prettyprint ;" "{ 1 2 3 } std ." "1.0" } { $example "USING: math.statistics prettyprint ;" "{ 1 2 3 4 } std ." "1.290994448735806" } } ; HELP: ste { $values { "seq" "a sequence of numbers" } { "x" "a non-negative real number"} } - { $description "Computes the standard error of the mean for " { $snippet "seq" } ". It's defined as the standard deviation divided by the square root of the length of the sequence, and measures uncertainty associated with the estimate of the mean." } + { $description "Computes the standard error of the mean for " { $snippet "seq" } ". It's defined as the standard deviation divided by the square root of the length of the sequence, and measures uncertainty associated with the estimate of the mean." } { $examples { $example "USING: math.statistics prettyprint ;" "{ -2 2 } ste ." "2.0" } { $example "USING: math.statistics prettyprint ;" "{ -2 2 2 } ste ." "1.333333333333333" } } ; HELP: var { $values { "seq" "a sequence of numbers" } { "x" "a non-negative real number"} } -{ $description "Computes the variance of " { $snippet "seq" } ". It's a measurement of the spread of values in a sequence. The larger the variance, the larger the distance of values from the mean." } +{ $description "Computes the variance of " { $snippet "seq" } ". It's a measurement of the spread of values in a sequence. The larger the variance, the larger the distance of values from the mean." } { $notes "If the number of elements in " { $snippet "seq" } " is 1 or less, it outputs 0." } { $examples { $example "USING: math.statistics prettyprint ;" "{ 1 } var ." "0" } diff --git a/extra/math/statistics/statistics.factor b/extra/math/statistics/statistics.factor index 7568af5294..d2494ee32a 100644 --- a/extra/math/statistics/statistics.factor +++ b/extra/math/statistics/statistics.factor @@ -5,20 +5,15 @@ USING: arrays combinators kernel math math.analysis math.functions sequences IN: math.statistics : mean ( seq -- n ) - #! arithmetic mean, sum divided by length [ sum ] [ length ] bi / ; : geometric-mean ( seq -- n ) - #! geometric mean, nth root of product [ length ] [ product ] bi nth-root ; : harmonic-mean ( seq -- n ) - #! harmonic mean, reciprocal of sum of reciprocals. - #! positive reals only [ recip ] sigma recip ; : median ( seq -- n ) - #! middle number if odd, avg of two middle numbers if even natural-sort dup length even? [ [ midpoint@ dup 1- 2array ] keep nths mean ] [ @@ -26,11 +21,10 @@ IN: math.statistics ] if ; : range ( seq -- n ) - #! max - min minmax swap - ; : var ( seq -- x ) - #! variance, normalize by N-1 + #! normalize by N-1 dup length 1 <= [ drop 0 ] [ @@ -39,11 +33,9 @@ IN: math.statistics ] if ; : std ( seq -- x ) - #! standard deviation, sqrt of variance var sqrt ; : ste ( seq -- x ) - #! standard error, standard deviation / sqrt ( length of sequence ) [ std ] [ length ] bi sqrt / ; : ((r)) ( mean(x) mean(y) {x} {y} -- (r) )