FME Transformers: 2024.1

Categories
Calculated Values

DensityCalculator

Determines the density of a group of Candidate features.

How does it work?

Density is a measurement of Candidate values per unit area. It is calculated as a numeric value; the greater the value, the more dense are the Candidate features.

The density equation is Total Candidates/Area of Interest.

Total Candidates is defined by either:

  • The total NUMBER of Candidate features
  • The sum LENGTH of Candidate features
  • The sum Area of Candidate features

Area of Interest is defined by the size of the first polygon feature that enters the Area input port.

Caution

It’s VERY important to note that ALL Candidate features count towards the density calculation, even if they fall outside the Area feature.

In other words, this transformer does not test whether or not candidate objects are inside the Area feature. If you wish to use only Candidate features that lie within, or overlap, the Area feature, you should pre-process the data using either a SpatialFilter or SpatialRelator transformer.

Usage Notes

  • The geometry type of Candidate features may be points, lines, or polygons. However, Area features must be polygons.
  • If excess Area features are supplied – that is, there is more than one Area feature for a particular group – then they are excluded from the calculation of density for Candidates. However, they will still receive their own density calculation. In other words, each Area receives the density of Candidate features for their own size; but Candidate features only receive their density in relation to the size of the first Area feature.
  • If you need to find the density of Candidate features against the total area of a number of polygon features, use an Aggregator to aggregate the polygons and input the resulting aggregate to the Area port of this transformer.

Configuration

Input Ports

Output Ports

Parameters

Editing Transformer Parameters

Transformer parameters can be set by directly entering values, using expressions, or referencing other elements in the workspace such as attribute values or user parameters. Various editors and context menus are available to assist. To see what is available, click beside the applicable parameter.

For more information, see Transformer Parameter Menu Options.

Related Transformers

SpatialRelator

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