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89 lines
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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Purpose and usage</title><link rel="stylesheet" type="text/css" href="manual.css"><meta name="generator" content="DocBook XSL Stylesheets V1.76.0"><link rel="home" href="index.html" title="JpGraph Manual"><link rel="up" href="ch01.html" title="Chapter 1. About the library"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Purpose and usage</th></tr><tr><td width="20%" align="left"> </td><th width="60%" align="center">Chapter 1. About the library</th><td width="20%" align="right"> </td></tr></table><hr></div><div class="sect1" title="Purpose and usage"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2472320"></a>Purpose and usage</h2></div></div></div>
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<p>The purpose of the library is to make it possible to (very) easily create dynamic
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images (a.k.a. graphs) using PHP scripting. The library hides as much as possible
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all the details necessary to create dynamic images. Strictly speaking all the basic
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low level functionality to draw images are already available in PHP since PHP comes
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with the core GD library which is the very lowest layer to create images. The GD
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library has graphic primitives to create lines, circles, points etc. but it has no
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built-in intelligence to handle scales, labelling , colors etc. This logically makes
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JpGraph library a higher type library more easily accessible than the raw GD
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library. </p>
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<div class="figure"><a name="id2472478"></a><p class="title"><b>Figure 1.1. JpGraph and PHP</b></p><div class="figure-contents">
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<div class="mediaobject"><img src="images/jpgraph-and-php.png" alt="JpGraph and PHP"></div>
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</div></div><br class="figure-break">
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<p>There are several possible usage scenario for the library and it's different
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parts. </p>
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<p>The most common usage is most likely to visualize numeric data by creating basic
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charts (for example line, bar or pie charts) that is included dynamically in a
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WEB-page via a straight forward <code class="code"><img></code> tag. The details on how to
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create dynamic graphs will be fully covered in later sections of this manual The
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library itself is agnostic to where the data comes from so it could for example be
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retrieved from a database, from a plain text file or perhaps from some WEB-service.
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In addition to this scenario the library could be used as a tool to create dynamic
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charts that are stored as image files in a directory. This makes it possible to use
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the library in an off-line batch mode from the command line (most likely using the
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cli =command line version of PHP). For an example of using JpGraph in batch mode see <a class="xref" href="ch34.html" title="Chapter 34. Showing SPAM statistics">Chapter 34. <i>Showing SPAM statistics</i></a>.</p>
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<p>In addition to these basic usage scenarios both the free and the slightly more
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advanced pro-version of the library includes a multitude of additional functionality
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which includes for example more advanced graph types (like spider graphs, polar
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plots, contour plots etc.) and some non graph capabilities like the possibility to
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create barcodes (only available in the pro-version) or to create Gantt-charts. The
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usage of all of these types of graphs are explained in this manual.</p>
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<p>
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</p><div class="caution" title="Caution" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Caution</h3>
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<p>In order to use JpGraph the PHP installation must have support for the GD
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libraries enabled. See Chapter 2 and 3 for details on checking the
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installation.</p>
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</div><p>
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</p>
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<p>In order to get a quick feel for how the library can be used we have included in <a class="xref" href="ch01s04.html#example.example0" title="Example 1.1. This is the very first example (example0.php)">Example 1.1. This is the very first example (<code class="filename">example0.php</code>) </a> a very basic type of line graph. Don't worry
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right now about the details, the message here is that it only takes six lines of
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real script code to create a basic graph. Have a look at the example and see just
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how much of the script makes sense without us even having discussed any API
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yet.</p>
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<div class="example"><a name="example.example0"></a><p class="title"><b>Example 1.1. This is the very first example (<code class="filename">example0.php</code>) </b></p><div class="example-contents"> <div class="hl-main"><table class="hl-table" width="100%"><tr><td class="hl-gutter" align="right" valign="top"><pre>1
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</pre></td><td class="hl-main" valign="top"><pre><span class="hl-inlinetags"><?php</span><span class="hl-code"> </span><span class="hl-comment">//</span><span class="hl-comment"> content="text/plain; charset=utf-8"</span><span class="hl-comment"></span><span class="hl-code">
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</span><span class="hl-reserved">require_once</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-quotes">'</span><span class="hl-string">jpgraph/jpgraph.php</span><span class="hl-quotes">'</span><span class="hl-brackets">)</span><span class="hl-code">;
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</span><span class="hl-reserved">require_once</span><span class="hl-code"> </span><span class="hl-brackets">(</span><span class="hl-quotes">'</span><span class="hl-string">jpgraph/jpgraph_line.php</span><span class="hl-quotes">'</span><span class="hl-brackets">)</span><span class="hl-code">;
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</span><span class="hl-comment">//</span><span class="hl-comment"> Some data</span><span class="hl-comment"></span><span class="hl-code">
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</span><span class="hl-var">$ydata</span><span class="hl-code"> = </span><span class="hl-reserved">array</span><span class="hl-brackets">(</span><span class="hl-number">11</span><span class="hl-code">,</span><span class="hl-number">3</span><span class="hl-code">,</span><span class="hl-number">8</span><span class="hl-code">,</span><span class="hl-number">12</span><span class="hl-code">,</span><span class="hl-number">5</span><span class="hl-code">,</span><span class="hl-number">1</span><span class="hl-code">,</span><span class="hl-number">9</span><span class="hl-code">,</span><span class="hl-number">13</span><span class="hl-code">,</span><span class="hl-number">5</span><span class="hl-code">,</span><span class="hl-number">7</span><span class="hl-brackets">)</span><span class="hl-code">;
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</span><span class="hl-comment">//</span><span class="hl-comment"> Create the graph. These two calls are always required</span><span class="hl-comment"></span><span class="hl-code">
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</span><span class="hl-var">$graph</span><span class="hl-code"> = </span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">Graph</span><span class="hl-brackets">(</span><span class="hl-number">350</span><span class="hl-code">,</span><span class="hl-number">250</span><span class="hl-brackets">)</span><span class="hl-code">;
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</span><span class="hl-var">$graph</span><span class="hl-code">-></span><span class="hl-identifier">SetScale</span><span class="hl-brackets">(</span><span class="hl-quotes">'</span><span class="hl-string">textlin</span><span class="hl-quotes">'</span><span class="hl-brackets">)</span><span class="hl-code">;
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</span><span class="hl-comment">//</span><span class="hl-comment"> Create the linear plot</span><span class="hl-comment"></span><span class="hl-code">
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</span><span class="hl-var">$lineplot</span><span class="hl-code">=</span><span class="hl-reserved">new</span><span class="hl-code"> </span><span class="hl-identifier">LinePlot</span><span class="hl-brackets">(</span><span class="hl-var">$ydata</span><span class="hl-brackets">)</span><span class="hl-code">;
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</span><span class="hl-var">$lineplot</span><span class="hl-code">-></span><span class="hl-identifier">SetColor</span><span class="hl-brackets">(</span><span class="hl-quotes">'</span><span class="hl-string">blue</span><span class="hl-quotes">'</span><span class="hl-brackets">)</span><span class="hl-code">;
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</span><span class="hl-comment">//</span><span class="hl-comment"> Add the plot to the graph</span><span class="hl-comment"></span><span class="hl-code">
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</span><span class="hl-var">$graph</span><span class="hl-code">-></span><span class="hl-identifier">Add</span><span class="hl-brackets">(</span><span class="hl-var">$lineplot</span><span class="hl-brackets">)</span><span class="hl-code">;
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</span><span class="hl-comment">//</span><span class="hl-comment"> Display the graph</span><span class="hl-comment"></span><span class="hl-code">
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</span><span class="hl-var">$graph</span><span class="hl-code">-></span><span class="hl-identifier">Stroke</span><span class="hl-brackets">(</span><span class="hl-brackets">)</span><span class="hl-code">;
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</span><span class="hl-inlinetags">?></span></pre></td></tr></table></div></div></div><br class="example-break"> <div class="figure"><a name="fig.example0"></a><p class="title"><b>Figure 1.2. This is the very first example <code class="uri"><a class="uri" href="example_src/example0.html" target="_top">(<code class="filename">example0.php</code>)</a></code> </b></p><div class="figure-contents"> <span class="inlinemediaobject"><img src="images/example0.png" alt="This is the very first example (example0.php)"></span> </div></div><br class="figure-break">
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