Category: Helper -> Community | Category:Helper -> Charts
Introduction
The purpose of the gchart helper is to provide functions to help with the use of Google’s chart api.
Currently, the only function in the helper is extendedencode(). To use the gChart api, one generates a series of HTTP GET parameters attached to a google url, which returns an image. The most complicated part of generating this url is encoding the data that represents the chart. This helper makes that easy.
Source
<?php if (!defined('BASEPATH')) exit('No direct script access allowed');
/**
* CodeIgniter
*
* An open source application development framework for PHP 4.3.2 or newer
*
* @package CodeIgniter
* @author Rick Ellis
* @copyright Copyright (c) 2006, EllisLab, Inc.
* @license http://www.codeigniter.com/user_guide/license.html
* @link http://www.codeigniter.com
* @since Version 1.0
* @filesource
*/
/**
* CodeIgniter gChart Helper
*
* @package CodeIgniter
* @subpackage Helpers
* @category Helpers
* @author Isaac Vetter
*/
/**
* ExtendedEncode
*
* Encodes an array of values using the extended encoding:
* http://code.google.com/apis/chart/#extended_values
* @access public
* @param array
* @param referencedstring
* @return string
*/
function extendedencode($data, &$maxvalue='notspecified')
{
$grid = array('A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I',
'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k',
'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y',
'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '-', '.');
// try to find reasonable maximum value
if(is_numeric($maxvalue)){
// assume below manipulations are better than what caller is doing
$max = ceil($maxvalue);
} else {
$max = ceil(max($data));
}
$precision = strlen($max) - 1;
$maxvalue = ceil($max/pow(10,$precision));
$maxvalue = $maxvalue * pow(10, $precision);
$multiplier = (float)(count($grid) * count($grid)) / $maxvalue;
$ret = '';
for($i=0;$i<count($data);$i++){
if(!is_numeric($data[$i])){
$ret .= '__';
} else {
$datum = $data[$i] * $multiplier;
$x = (int)($datum / count($grid));
$y = $datum % 64;
$ret .= $grid[$x].$grid[$y];
}
}
return $ret;
}
?>
Usage
Here’s an example of how to use this helper to generate a chart. To begin using it, add the following code to your controller:
$this->load->helper( 'gchart' );
Next, add the following bit of code to your view where you would like to display the chart:
<?php
$encoded_data = extendedencode(array(0, 1, 2, 3, 4, 5, 6), &maxvalue;);
echo <<< EOS
<img src="
http://chart.apis.google.com/chart?
cht=lc
&chs=250x250
&chd;:e{$encoded}
"
alt="line graph of some example data"
/>
EOS;
?>
The above code generate this url as the img src:
http://chart.apis.google.com/chart?cht=lc&chs=250x250&chd=e:AAKqVVgAqq1VA
Which looks like this:
The Google Chart API is pretty awesome. The above really doesn’t do it justice. You should read the Google documentation.
Here’s a more complicated example:
<?php
$encoded = extendedencode(array(3.6, 1, 2, 1.5, 4.0, 5.6, 2.3), &$maxvalue);
$halfmaxvalue = $maxvalue / 2;
$chart = <<< EOS
<img src="
http://chart.apis.google.com/chart?
cht=bvg
&chs=300x400
&chd=e:{$encoded}
&chxt=x,x,y,y
&chxl;=
0:|Jan|Feb|Mar|Apr|May|June|July|
1:||Months||
2:|0|{$halfmaxvalue}|{$maxvalue}|
3:||||(in bazillions)|Traffic||
&chf=c,ls,0,FFFFFF,.5,EEEEEE,.5
"
alt="line graph of some dummy example data"
/>
EOS;
print $chart;
?>
The above code generates this url as the img src:
http://chart.apis.google.com/chart?cht=bvg&chs=300x400&chd=e:mZKqVVQAqq7uYi&chts=b1946c,20&chxt=x,x,y,y&chxl=0:|Jan|Feb|Mar|Apr|May|June|July|1:||Months||2:|0|3|6|3:||||(in bazillions)|Traffic||&chf=c,ls,0,FFFFFF,.5,EEEEEE,.5
Which looks like this: