Cumulative standard deviation: Difference between revisions

=={{header|Factor}}==

<lang factor>USING: accessors io kernel math math.functions math.parser

sequences ;

IN: standard-deviator

TUPLE: standard-deviator sum sum^2 n ;

: <standard-deviator> ( -- standard-deviator )

0.0 0.0 0 standard-deviator boa ;

: current-std ( standard-deviator -- std )

[ [ sum^2>> ] [ n>> ] bi / ]

[ [ sum>> ] [ n>> ] bi / sq ] bi - sqrt ;

: add-value ( value standard-deviator -- )

[ nip [ 1 + ] change-n drop ]

[ [ + ] change-sum drop ]

[ [ [ sq ] dip + ] change-sum^2 drop ] 2tri ;

: main ( -- )

{ 2 4 4 4 5 5 7 9 }

<standard-deviator> [ [ add-value ] curry each ] keep

current-std number>string print ;</lang>