<?php
/*
* This is a histogram class that accepts and unidimensional array of data
* Returns 2 arrays by using the getStats() and getBins() methods.
* (c) Jesus M. Castagnetto, 1999.
* Gnu GPL'd code, see www.fsf.org for the details.
*/
class Histogram {
/* variables */
var $N,$MIN,$MAX,$AVG,$STDV,$SUM,$SUM2,$NBINS;
var $BINS = array();
var $BINGRAPH = array();
var $STATS = array();
/* Constructor */
function Histogram($data="", $nbins=0, $title="") {
if ($data && $nbins) {
$this->create($data,$nbins,$title);
}
}
/* Create the histogram */
function create($data,$nbins,$title="") {
/* Check if we got a valid set of data and bins */
(($this->N = count($data)) > 1) or die("Not enough data, number of values: ".$this->N."\n");
($this->NBINS = $nbins) > 1 or die("Insuficient number of bins\n");
/* initialize values */
$this->MIN = (float) min($data);
$this->MAX = (float) max($data);
$delta = (float) ($this->MAX - $this->MIN)/$this->NBINS;
$this->setTitle($title);
/* init bins array */
for ($i=0; $i < $this->NBINS; $i++) {
$bin[$i] = (float) $this->MIN + $delta * $i;
$this->BINS[ (string) $bin[$i] ] = 0;
}
/* stats */
for ($i = 0; $i < $this->N ; $i++) {
$this->SUM += (float) $data[$i];
$this->SUM2 += (float) pow($data[$i],2);
}
$this->AVG = $this->SUM/$this->N;
$this->STDV = sqrt(($this->SUM2 - $this->N*pow($this->AVG,2))/(float)($this->N - 1));
/* make the STATS array */
$this->STATS = array (
MIN=>$this->MIN,
MAX=>$this->MAX,
N=>$this->N,
SUM=>$this->SUM,
SUM2=>$this->SUM2,
AVG=>$this->AVG,
STDV=>$this->STDV,
NBINS=>$this->NBINS
);
/* calculate frequencies and populate bins array */
sort($data);
$tmp = ($this->NBINS - 1);
for ($i = 0; $i < $this->N; $i++) {
for ($j = $tmp; $j >= 0; $j--) {
if ($data[$i] >= $bin[$j]) {
$this->BINS[ (string) $bin[$j] ]++;
break;
}
}
}
}
/* sets the Title */
function setTitle($title) {
$this->TITLE=$title;
}
/* send back STATS array */
function getStats() {
return $this->STATS;
}
/* send back BINS array */
function getBins() {
return $this->BINS;
}
/* send back BINS array suitable for plotting with class.graph */
function getGraphBins() {
while (list($k,$v) = each($this->BINS)) {
$bin[] = sprintf("%5.2f",$k); $val[] = $v;
}
$bingraph = array($bin,$val);
return $bingraph;
}
/* simple printStats */
function printStats() {
$s = "Statistics for histogram: ".$this->TITLE."\n";
$s .= sprintf("N = %8d\t\tMin = %-8.4f\tMax = %-8.4f\tAvg = %-8.4f\n",$this->N,$this->MIN,$this->MAX,$this->AVG);
$s .= sprintf("StDev = %-8.4f\tSum = %-8.4f\tSum^2 = %-8.4f\n",$this->STDV,$this->SUM,$this->SUM2);
echo $s;
}
/* simple printBins */
function printBins() {
echo "Number of bins: ".count($this->BINS)."\n";
echo "BIN\tVAL\t\tFREQ\n";
$maxbin = max($this->BINS);
reset($this->BINS);
for ($i = 0; $i < $this->NBINS; $i++) {
list($key,$val) = each($this->BINS);
echo sprintf("%d\t%-8.4f\t%-8d |%s\n",$i+1,$key,$val,$this->_printBar($val,$maxbin));
}
}
/* internal function to generate the histogram bars */
function _printBar($val,$maxbin) {
$fact = (float) ($maxbin > 40) ? 40/$maxbin : 1;
$niter = (int) $val * $fact;
$out = "";
for ($i=0; $i<$niter; $i++)
$out .= "*";
return $out;
}
} /* end of Histogram class */
?>
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