Introduction (historical revision 20488)

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Still under testing!

Introduction

This library is a port of Larry Hunter's Lisp statistics library to chicken scheme.

The library provides a number of formulae and methods taken from the book "Fundamentals of Biostatistics" by Bernard Rosner (5th edition).

(random-pick items): given a list of items, returns a random item.
(random-sample n items): given a number of items to select, n, and a list of items to select from, items, returns a random sample without replacement of size n.
(sign n): given a number n, returns 0, 1 or -1 according to if n is zero, positive or negative.
(square n): given a number n, returns the square of n.

These functions provide information on a given list of numbers. Note, the list of items does not have to be sorted.

(mean items): given a list of numbers, items, returns the arithmetic mean of the items (the sum of the numbers divided by the number of numbers).

(mean '(1 2 3 4 5)) => 3

(median items): given a list of numbers, items, returns the value which separates the upper and lower halves of the list of numbers.

(median '(1 2 3 4)) => 5/2

(mode items)
(geometric-mean items): given a list of numbers, items, returns the geometric mean of the items (the result of multiplying the items together and then taking the nth root, where n is the number of items).

(geometric-mean '(1 2 3 4 5)) => 2.60517108469735

(range items): given a list of numbers, items, returns the difference between the biggest and the smallest value.

(range '(5 1 2 3 4)) => 4

(percentile items percent): given a list of numbers, items, and a percentage, percent, returns the item closest to the percent value if the items are sorted into order; the returned item may be in the list, or the average of adjacent values.

(percentile '(1 2 3 4) 50) => 5/2
(percentile '(1 2 3 4) 67) => 3

(variance items): given a list of numbers, items, returns the variance of the numbers.
(standard-deviation items): given a list of numbers, items, returns the standard deviation of the numbers.
(coefficient-of-variation items): given a list of numbers, items, returns 100 * (std-dev / mean) of the items.

(coefficient-of-variation '(1 2 3 4)) => 51.6397779494322

(standard-error-of-the-mean items): given a list of numbers, items, returns std-dev / sqrt(length items).

 (standard-error-of-the-mean '(1 2 3 4)) => 0.645497224367903

(mean-sd-n items): given a list of numbers, items, returns three values, one for the mean, one for the standard deviation, and one for the length of the list.

> (mean-sd-n '(1 2 3 4))
5/2
1.29099444873581
4

Peter Lane wrote the scheme version of this library. The original Lisp version was written by Larry Hunter.

GPL version 3.0.

Needs srfi-1, srfi-25, srfi-69, vector-lib, numbers, extras, foreign, format

Uses the GNU scientific library for basic numeric processing, so requires libgsl, libgslcblas and the development files for libgsl.

trunk, for testing