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<td >Qt 5.9</td><td ><a href="qtcharts-index.html">Qt Charts</a></td><td ><a href="qtcharts-examples.html">Qt Charts Examples</a></td><td >Polar Chart Example</td></tr></table><table class="buildversion"><tr>
<td id="buildversion" width="100%" align="right">Qt 5.9.4 Reference Documentation</td>
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<h3><a name="toc">Contents</a></h3>
<ul>
<li class="level1"><a href="#running-the-example">Running the Example</a></li>
<li class="level1"><a href="#creating-polar-charts">Creating Polar Charts</a></li>
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<h1 class="title">Polar Chart Example</h1>
<span class="subtitle"></span>
<!-- $$$polarchart-description -->
<div class="descr"> <a name="details"></a>
<p>It also shows how to implement scrolling and zooming of the polar chart as well as visually demonstrate how polar charts and cartesian charts relate to each other.</p>
<p class="centerAlign"><img src="images/examples_polarchart.png" alt="" /></p><a name="running-the-example"></a>
<h2 id="running-the-example">Running the Example</h2>
<p>To run the example from Qt Creator, open the <b>Welcome</b> mode and select the example from <b>Examples</b>. For more information, visit Building and Running an Example.</p>
<a name="creating-polar-charts"></a>
<h2 id="creating-polar-charts">Creating Polar Charts</h2>
<p>Creating a polar chart is done with a <a href="qpolarchart.html">QPolarChart</a> instance instead of a <a href="qchart.html">QChart</a> instance.</p>
<pre class="cpp">
<span class="type"><a href="qpolarchart.html">QPolarChart</a></span> <span class="operator">*</span>chart <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qpolarchart.html">QPolarChart</a></span>();
</pre>
<p>Axes are created similarly to cartesian charts, but when axes are added to the chart, you can use polar orientations instead of alignments.</p>
<pre class="cpp">
<span class="type"><a href="qvalueaxis.html">QValueAxis</a></span> <span class="operator">*</span>angularAxis <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qvalueaxis.html">QValueAxis</a></span>();
angularAxis<span class="operator">-</span><span class="operator">></span>setTickCount(<span class="number">9</span>); <span class="comment">// First and last ticks are co-located on 0/360 angle.</span>
angularAxis<span class="operator">-</span><span class="operator">></span>setLabelFormat(<span class="string">"%.1f"</span>);
angularAxis<span class="operator">-</span><span class="operator">></span>setShadesVisible(<span class="keyword">true</span>);
angularAxis<span class="operator">-</span><span class="operator">></span>setShadesBrush(<span class="type">QBrush</span>(<span class="type">QColor</span>(<span class="number">249</span><span class="operator">,</span> <span class="number">249</span><span class="operator">,</span> <span class="number">255</span>)));
chart<span class="operator">-</span><span class="operator">></span>addAxis(angularAxis<span class="operator">,</span> <span class="type"><a href="qpolarchart.html">QPolarChart</a></span><span class="operator">::</span>PolarOrientationAngular);
<span class="type"><a href="qvalueaxis.html">QValueAxis</a></span> <span class="operator">*</span>radialAxis <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qvalueaxis.html">QValueAxis</a></span>();
radialAxis<span class="operator">-</span><span class="operator">></span>setTickCount(<span class="number">9</span>);
radialAxis<span class="operator">-</span><span class="operator">></span>setLabelFormat(<span class="string">"%d"</span>);
chart<span class="operator">-</span><span class="operator">></span>addAxis(radialAxis<span class="operator">,</span> <span class="type"><a href="qpolarchart.html">QPolarChart</a></span><span class="operator">::</span>PolarOrientationRadial);
</pre>
<p>Zooming and scrolling of a polar chart is logically nearly identical to zooming and scrolling of a cartesian chart. The main difference is that when scrolling along the X-axis (angular axis), the angle is used instead of the number of pixels. Another difference is that zooming to a rectangle cannot be done.</p>
<pre class="cpp">
<span class="type">void</span> ChartView<span class="operator">::</span>keyPressEvent(<span class="type">QKeyEvent</span> <span class="operator">*</span>event)
{
<span class="keyword">switch</span> (event<span class="operator">-</span><span class="operator">></span>key()) {
<span class="keyword">case</span> <span class="type">Qt</span><span class="operator">::</span>Key_Plus:
chart()<span class="operator">-</span><span class="operator">></span>zoomIn();
<span class="keyword">break</span>;
<span class="keyword">case</span> <span class="type">Qt</span><span class="operator">::</span>Key_Minus:
chart()<span class="operator">-</span><span class="operator">></span>zoomOut();
<span class="keyword">break</span>;
<span class="keyword">case</span> <span class="type">Qt</span><span class="operator">::</span>Key_Left:
chart()<span class="operator">-</span><span class="operator">></span>scroll(<span class="operator">-</span><span class="number">1.0</span><span class="operator">,</span> <span class="number">0</span>);
<span class="keyword">break</span>;
<span class="keyword">case</span> <span class="type">Qt</span><span class="operator">::</span>Key_Right:
chart()<span class="operator">-</span><span class="operator">></span>scroll(<span class="number">1.0</span><span class="operator">,</span> <span class="number">0</span>);
<span class="keyword">break</span>;
<span class="keyword">case</span> <span class="type">Qt</span><span class="operator">::</span>Key_Up:
chart()<span class="operator">-</span><span class="operator">></span>scroll(<span class="number">0</span><span class="operator">,</span> <span class="number">1.0</span>);
<span class="keyword">break</span>;
<span class="keyword">case</span> <span class="type">Qt</span><span class="operator">::</span>Key_Down:
chart()<span class="operator">-</span><span class="operator">></span>scroll(<span class="number">0</span><span class="operator">,</span> <span class="operator">-</span><span class="number">1.0</span>);
<span class="keyword">break</span>;
<span class="keyword">case</span> <span class="type">Qt</span><span class="operator">::</span>Key_Space:
switchChartType();
<span class="keyword">break</span>;
<span class="keyword">default</span>:
<span class="type">QGraphicsView</span><span class="operator">::</span>keyPressEvent(event);
<span class="keyword">break</span>;
}
}
</pre>
<p>The same axes and series can be used in both cartesian and polar charts, though not simultaneously. To switch between chart types, you first need to remove the series and axes from the old chart, and then add them to the new chart. If you want to preserve the axis ranges, those need to be copied, too.</p>
<pre class="cpp">
<span class="type">void</span> ChartView<span class="operator">::</span>switchChartType()
{
<span class="type"><a href="qchart.html">QChart</a></span> <span class="operator">*</span>newChart;
<span class="type"><a href="qchart.html">QChart</a></span> <span class="operator">*</span>oldChart <span class="operator">=</span> chart();
<span class="keyword">if</span> (oldChart<span class="operator">-</span><span class="operator">></span>chartType() <span class="operator">=</span><span class="operator">=</span> <span class="type"><a href="qchart.html">QChart</a></span><span class="operator">::</span>ChartTypeCartesian)
newChart <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qpolarchart.html">QPolarChart</a></span>();
<span class="keyword">else</span>
newChart <span class="operator">=</span> <span class="keyword">new</span> <span class="type"><a href="qchart.html">QChart</a></span>();
<span class="comment">// Move series and axes from old chart to new one</span>
<span class="keyword">const</span> <span class="type">QList</span><span class="operator"><</span><span class="type"><a href="qabstractseries.html">QAbstractSeries</a></span> <span class="operator">*</span><span class="operator">></span> seriesList <span class="operator">=</span> oldChart<span class="operator">-</span><span class="operator">></span>series();
<span class="keyword">const</span> <span class="type">QList</span><span class="operator"><</span><span class="type"><a href="qabstractaxis.html">QAbstractAxis</a></span> <span class="operator">*</span><span class="operator">></span> axisList <span class="operator">=</span> oldChart<span class="operator">-</span><span class="operator">></span>axes();
<span class="type">QList</span><span class="operator"><</span><span class="type">QPair</span><span class="operator"><</span><span class="type">qreal</span><span class="operator">,</span> <span class="type">qreal</span><span class="operator">></span> <span class="operator">></span> axisRanges;
<span class="keyword">for</span> (<span class="type"><a href="qabstractaxis.html">QAbstractAxis</a></span> <span class="operator">*</span>axis : axisList) {
<span class="type"><a href="qvalueaxis.html">QValueAxis</a></span> <span class="operator">*</span>valueAxis <span class="operator">=</span> <span class="keyword">static_cast</span><span class="operator"><</span><span class="type"><a href="qvalueaxis.html">QValueAxis</a></span> <span class="operator">*</span><span class="operator">></span>(axis);
axisRanges<span class="operator">.</span>append(<span class="type">QPair</span><span class="operator"><</span><span class="type">qreal</span><span class="operator">,</span> <span class="type">qreal</span><span class="operator">></span>(valueAxis<span class="operator">-</span><span class="operator">></span>min()<span class="operator">,</span> valueAxis<span class="operator">-</span><span class="operator">></span>max()));
}
<span class="keyword">for</span> (<span class="type"><a href="qabstractseries.html">QAbstractSeries</a></span> <span class="operator">*</span>series : seriesList)
oldChart<span class="operator">-</span><span class="operator">></span>removeSeries(series);
<span class="keyword">for</span> (<span class="type"><a href="qabstractaxis.html">QAbstractAxis</a></span> <span class="operator">*</span>axis : axisList) {
oldChart<span class="operator">-</span><span class="operator">></span>removeAxis(axis);
newChart<span class="operator">-</span><span class="operator">></span>addAxis(axis<span class="operator">,</span> axis<span class="operator">-</span><span class="operator">></span>alignment());
}
<span class="keyword">for</span> (<span class="type"><a href="qabstractseries.html">QAbstractSeries</a></span> <span class="operator">*</span>series : seriesList) {
newChart<span class="operator">-</span><span class="operator">></span>addSeries(series);
<span class="keyword">for</span> (<span class="type"><a href="qabstractaxis.html">QAbstractAxis</a></span> <span class="operator">*</span>axis : axisList)
series<span class="operator">-</span><span class="operator">></span>attachAxis(axis);
}
<span class="type">int</span> count <span class="operator">=</span> <span class="number">0</span>;
<span class="keyword">for</span> (<span class="type"><a href="qabstractaxis.html">QAbstractAxis</a></span> <span class="operator">*</span>axis : axisList) {
axis<span class="operator">-</span><span class="operator">></span>setRange(axisRanges<span class="operator">[</span>count<span class="operator">]</span><span class="operator">.</span>first<span class="operator">,</span> axisRanges<span class="operator">[</span>count<span class="operator">]</span><span class="operator">.</span>second);
count<span class="operator">+</span><span class="operator">+</span>;
}
newChart<span class="operator">-</span><span class="operator">></span>setTitle(oldChart<span class="operator">-</span><span class="operator">></span>title());
setChart(newChart);
<span class="keyword">delete</span> oldChart;
}
</pre>
<p>Files:</p>
<ul>
<li><a href="qtcharts-polarchart-chartview-cpp.html">polarchart/chartview.cpp</a></li>
<li><a href="qtcharts-polarchart-chartview-h.html">polarchart/chartview.h</a></li>
<li><a href="qtcharts-polarchart-main-cpp.html">polarchart/main.cpp</a></li>
<li><a href="qtcharts-polarchart-polarchart-pro.html">polarchart/polarchart.pro</a></li>
</ul>
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<!-- @@@polarchart -->
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Mageia
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x86_64
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core-updates
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