The Chart widget displays quantitative attributes from a map layer as a graphical representation of data. It is designed to make it easy for end users to observe possible patterns and trends in quantitative attribute data, as charts can usually be read more quickly than the raw data that they are produced from.
When the widget is activated, the end user needs to provide 2 inputs to run the widget:
- Select the data layer from which to retrieve the data from, and
- Select a graphical spatial search tool, then provide an input selection on the map display.
In the graphic below, the USA Diversity Index layer and the Draw Freehand Polygon spatial search tool are selected. Eight northeastern states are selected in the map.
Clicking Results will display the Chart widget results, in this case a bar chart that shows each selected state’s diversity index value. Hovering the cursor over each individual bar will display the state name and the diversity index value.
The Chart widget supports the display of four different chart types: bar chart, column chart, line chart, and pie chart. As with the bar chart, hovering the cursor over a chart element will display some additional information as a pop up.
The Chart widget also provides some simple statistical operators that can be applied for an attribute field. The statistical operators are: AVERAGE, COUNT, MAX, MIN, and SUM. Using the previous USA Diversity Index layer example, the Chart widget could have also displayed the average diversity index value of the eight selected states at the bottom of the Chart widget dialog.
The chart widget supports 2 types of input sources:
- Feature layer that is present in the map, usually because it has been added as an operational layer. Just specify the same name as used in the config.xml.
- Feature layer that is not already present in the map. This layer needs to support query capability and can be any layer from either a Map Service or Feature Service. You'll need to specify the URL of the layer.
The quantitative attributes and type of chart displayed by the Chart widget will need to be preconfigured in the widget configuration file, for each data layer. Multiple quantitative attributes can be specified for the same data layer, each with their own unique chart display. If multiple charts are available, the widget will display a ‘scroll’ arrow on the each side of the chart, and a counter in the lower right corner indicating the number of charts available.