Histogram

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

For instance, you want to plot the data distribution of numeric attributes of a feature collection. Then you can use a histogram with a suitable number of buckets to visualize and assess this.

Errors

The operator returns an error if the selected column (columnName) does not exist or is not numeric.

Notes

If bounds or buckets are not defined, the operator will determine these values by itself which requires processing the data twice.

If the buckets parameter is set to squareRootChoiceRule, the operator estimates it using the square root of the number of elements in the data.

Parameters

Name	Type	Description	Examples
columnName	string	Name of the (numeric) vector attribute or raster band to compute the histogram on.	"temperature"
bounds	HistogramBounds	If data, it computes the bounds of the underlying data. If { "min": ..., "max": ... }, one can specify custom bounds.
buckets	HistogramBuckets	The number of buckets. The value can be specified or calculated.
interactive	boolean	Flag, if the histogram should have user interactions for a range selection. It is false by default.	true

Sources

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

Examples

{
    "type": "Histogram",
    "params": {
        "columnName": "foobar",
        "bounds": {
            "min": 5,
            "max": 10
        },
        "buckets": {
            "type": "number",
            "value": 15
        },
        "interactive": false
    },
    "sources": {
        "vector": {
            "type": "OgrSource",
            "params": {
                "data": "ndvi"
            }
        }
    }
}