Created
November 11, 2010 14:53
-
-
Save djpowell/672592 to your computer and use it in GitHub Desktop.
fingertree stats
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
(ns finger-tree-stats | |
(:use [clojure.data.finger-tree])) | |
(defrecord stats [^double number ^double mean ^double variance]) | |
(def null-stats (stats. 0 0 Double/NaN)) | |
(defn make-stats | |
[^double x] | |
(stats. 1 x 0)) | |
(defn combine-stats | |
[nmv1 nmv2] | |
(let [{n1 :number m1 :mean v1 :variance} nmv1 | |
{n2 :number m2 :mean v2 :variance} nmv2] | |
(cond | |
(== n2 0) nmv1 | |
(== n1 0) nmv2 | |
:else | |
(let [delta (- m2 m1)] | |
(stats. | |
(+ n1 n2) | |
(/ (+ (* n1 m1) (* n2 m2)) (+ n1 n2)) | |
(+ v1 v2 (/ (* delta delta n1 n2) (+ n1 n2)))))))) | |
(def empty-stats-tree (finger-tree (meter make-stats null-stats combine-stats))) | |
; test | |
(def st (into empty-stats-tree [9.0 3.0 4.0 5.0 1.0 1.0 1.0 0.0 99.0 99.0])) | |
(println st) | |
(println (measured st)) | |
(println (measured (pop (rest st)))) | |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Compute statistics using a finger-tree.
Based on: http://blog.sigfpe.com/2010/11/statistical-fingertrees.html