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<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><title>5.22. Example - Annotating a Plot Using a Callback</title><link rel="stylesheet" type="text/css" href="phplotdoc.css" /><meta name="generator" content="DocBook XSL Stylesheets V1.78.1" /><link rel="home" href="index.html" title="PHPlot Reference Manual" /><link rel="up" href="examples.html" title="Chapter 5. PHPlot Examples" /><link rel="prev" href="ex-stackedarea1.html" title="5.21. Example - Stacked Area Plot" /><link rel="next" href="ex-webform.html" title="5.23. Example - Complete Web Form with Plot" /></head><body><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">5.22. Example - Annotating a Plot Using a Callback</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ex-stackedarea1.html">Prev</a> </td><th width="60%" align="center">Chapter 5. PHPlot Examples</th><td width="20%" align="right"> <a accesskey="n" href="ex-webform.html">Next</a></td></tr></table><hr /></div><div class="sect1"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a id="ex-annotate"></a>5.22. Example - Annotating a Plot Using a Callback</h2></div></div></div><p>
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This is an advanced example that uses a drawing callback to
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add annotations to a plot. More information on this topic can
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be found in <a class="xref" href="callbacks.html#callbacks-drawing" title="4.4.5. Using Callbacks to Annotate Plots">Section 4.4.5, “Using Callbacks to Annotate Plots”</a>,
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where this example is described in detail.
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</p><div class="example"><a id="example-annotate"></a><p class="title"><strong>Example 5.22. Annotated Plot</strong></p><div class="example-contents"><div class="informalfigure"><div class="mediaobject"><img src="examples/annotate.png" alt="Annotated Plot Example" /></div></div><pre class="programlisting"><?php
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# PHPlot Example: Annotating a plot using callbacks
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# Note: This example is coded for PHPlot > 5.0.7
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require_once 'phplot.php';
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# Get the Sales data. In real life, this would most likely come from
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# a database or external file. For this example, we will use 'random'
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# data, but with a fixed seed for repeatable results.
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function get_data()
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{
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mt_srand(1);
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$data = array();
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# Build an array with 12 arrays of (month_name, value):
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for ($month = 1; $month <= 12; $month++)
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$data[] = array(strftime('%b', mktime(12, 0, 0, $month, 1)),
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5 + mt_rand(5, 40));
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return $data;
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}
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# Find the best and worst sales data.
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# Gets the Y value (sales data) and X value. For PHPlot text-data data,
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# the X values are assigned as 0.5, 1.5, 2.5, etc.
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# The data array is in 'text-data' format: array of array(label, Y)...
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function get_best_worst($data,
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&$best_index, &$best_sales, &$worst_index, &$worst_sales)
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{
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$best_sales = NULL;
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$worst_sales = NULL;
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foreach ($data as $x => $point) {
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if (!isset($best_sales) || $point[1] > $best_sales) {
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$best_sales = $point[1];
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$best_index = $x + 0.5;
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}
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if (!isset($worst_sales) || $point[1] < $worst_sales) {
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$worst_sales = $point[1];
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$worst_index = $x + 0.5;
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}
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}
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}
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# Plot annotation callback.
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# The pass-through argument is the PHPlot object.
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function annotate_plot($img, $plot)
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{
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global $best_index, $best_sales, $worst_index, $worst_sales;
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# Allocate our own colors, rather than poking into the PHPlot object:
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$red = imagecolorresolve($img, 255, 0, 0);
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$green = imagecolorresolve($img, 0, 216, 0);
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# Get the pixel coordinates of the data points for the best and worst:
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list($best_x, $best_y) = $plot->GetDeviceXY($best_index, $best_sales);
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list($worst_x, $worst_y) = $plot->GetDeviceXY($worst_index, $worst_sales);
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# Draw ellipses centered on those two points:
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imageellipse($img, $best_x, $best_y, 50, 20, $green);
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imageellipse($img, $worst_x, $worst_y, 50, 20, $red);
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# Place some text above the points:
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$font = '3';
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$fh = imagefontheight($font);
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$fw = imagefontwidth($font);
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imagestring($img, $font, $best_x-$fw*4, $best_y-$fh-10,
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'Good Job!', $green);
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# We can also use the PHPlot internal function for text.
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# It does the center/bottom alignment calculations for us.
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# Specify the font argument as NULL or '' to use the generic one.
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$plot->DrawText('', 0, $worst_x, $worst_y-10, $red,
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'Bad News!', 'center', 'bottom');
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}
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# Begin main processing:
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# Fill the data array:
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$data = get_data();
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# Find the best and worst months:
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get_best_worst($data, $best_index, $best_sales, $worst_index, $worst_sales);
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# Create the PHPlot object, set title, plot type, data array type, and data:
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$plot = new PHPlot(800, 600);
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$plot->SetTitle('Monthly Widget Sales');
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$plot->SetPlotType('bars');
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$plot->SetDataType('text-data');
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$plot->SetDataValues($data);
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# Borders are needed for the manual:
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$plot->SetImageBorderType('plain');
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# Select X data labels (not tick labels):
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$plot->SetXTickPos('none');
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$plot->SetXTickLabelPos('none');
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$plot->SetXDataLabelPos('plotdown');
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# Format Y labels as "$nM" with no decimals, steps of 5:
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$plot->SetYLabelType('data', 0, '$', 'M');
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$plot->SetYTickIncrement(5.0);
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# Force the bottom of the plot to be at Y=0, and omit
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# the bottom "$0M" tick label because it looks odd:
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$plot->SetPlotAreaWorld(NULL, 0);
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$plot->SetSkipBottomTick(True);
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# Establish the drawing callback to do the annotation:
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$plot->SetCallback('draw_all', 'annotate_plot', $plot);
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# Draw the graph:
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$plot->DrawGraph();
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</pre></div></div><br class="example-break" /></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ex-stackedarea1.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="examples.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ex-webform.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">5.21. Example - Stacked Area Plot </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> 5.23. Example - Complete Web Form with Plot</td></tr></table></div></body></html>
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