median ( seq -- x )
Statistics

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Vocabulary
math.statistics

Inputs

seq	a sequence

Outputs

x	a non-negative real number

Word description
Computes the median of seq by finding the middle element of the sequence using kth-smallest. If there is an even number of elements in the sequence, the median is not unique, so the mean of the two middle values is output.

Examples

USING: math.statistics prettyprint ; { 1 2 3 } median .
2

USING: math.statistics prettyprint ; { 1 2 3 4 } median .
2+1/2

Errors
Throws a signal-error. (divide by zero) if the sequence is empty.

Definition

USING: kernel math sequences ;

IN: math.statistics

: median ( seq -- x )
    dup length odd? [ lower-median ] [ medians + 2 / ] if ;