ClassHistogram

The ClassHistogram is a plot operator that computes a histogram plot either over categorical attributes of a vector dataset or categorical values of a raster source. The output is a plot in Vega-Lite specification.

For instance, you want to plot the frequencies of the classes of a categorical attribute of a feature collection. Then you can use a class histogram to visualize and assess this.

Errors

The operator returns an error if…

• the selected column (columnName) does not exist or is not numeric,
• the source is a raster and the property columnName is set, or
• the input Measurement is not categorical.

The operator returns an error if

Notes

The operator only uses values of the categorical Measurement. It ignores missing or no-data values and values that are not covered by the Measurement.

Parameters

Name	Type	Description	Examples
columnName	string,null	The name of the attribute making up the x-axis of the histogram. Must be set for a vector sources, must not be set for rasters.	"class"

Sources

Name	Type	Description
source	SingleRasterOrVectorOperator	It is either a set of RasterOperator or a single VectorOperator

Examples

{
    "type": "ClassHistogram",
    "params": {
        "columnName": "class"
    },
    "sources": {
        "source": {
            "type": "OgrSource",
            "params": {
                "data": "landcover"
            }
        }
    }
}