The Vector Properties Dialog:Diagram Tab
Diagram Tab
The Diagram tab allows you to add a grahic overlay to a vector layer. To activate this feature, open the Plugin Manager and select the Diagram Overlay' plugin. After this, there is a new tab in the vector Layer Properties dialog where the settings for diagrams may be entered (see figure <A HREF="#fig:diagramtab">13</A>). <P>
[clip=true, width=13cm]diagram_tab
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<P> The current implementation of diagrams provides support for pie- and barcharts and for linear scaling of the diagram size according to a classification attribute. We will demonstrate an example and overlay the alaska boundary layer a barchart diagramm showing some temperature data from a climate vector layer. Both vector layers are part of the QGIS sample dataset (see Section <A HREF="#label_sampledata"><IMG ALIGN="BOTTOM" BORDER="1" ALT="[*]"
SRC="/usr/share/latex2html/icons/crossref.png"></A>.
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- First click on the mActionAddOgrLayerLoad Vector icon, browse to the QGIS sample dataset folder and load the two vector shape layers alaska.shp and climate.shp.
- Double click the climate layer in the map legend to open the Layer Properties dialog.
- Click on the Diagram Overlay and select Bar chart as Diagram type.
- In the diagram we want to display the values of the three columns T_F_JAN, T_F_JAN and T_F_MEAN. First select T_F_JAN as Attributes and click Add attribute, then T_F_JUL and finally T_F_MEAN.
- For linear scaling of the diagram size we define T_F_JUL as classification attribute.
- Now click on find maximum value, choose a size value and unit and click Apply to display the diagram in the QGIS main window.
- You can now adapt the chart size, or change the attribute colors double clicking on the color values in the attribute field. Figure <A HREF="#fig:climatediagram">14</A> gives an impression.
- Finally click Ok.
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[clip=true, width=13cm]climate_diagram
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