This tool can be used to calculate the related circumscribing circle (Mcgarigal et al. 2002) for polygon features. It works for either raster or vector input files. If a raster file is input, the grid should contain polygons with unique identifiers. Raster input files also require the name of the output raster file (where the related circumscribing circle will be assigned to each feature in the input file), the specified option of outputting text, and whether or not zero values should be treated as background values. If a vector shapefile is specified as the input file, the only required input is the name of the file. The related circumscribing circle values calculated for each vector polygon feature will be placed in the accompanying database file (.dbf) as a new field (RC_CIRCLE). The resulting database file will be automatically displayed after the tool has completed.
Related circumscribing circle (RCC) is defined as:
RCC = 1 - A / Ac
Where
A is the polygon's area and Ac the area of
the smallest circumscribing circle.
Theoretically, RCC ranges from 0 to 1, where a value of 0 indicates a circular polygon and a value of 1 indicates a highly elongated shape. The circumscribing circle provides a measure of polygon elongation. Unlike the elongation ratio, however, it does not provide a measure of polygon direction in addition to overall elongation. Like the Elongation Ratio and Linearity Index, RCC is not an adequate measure of overall polygon narrowness, because a highly sinuous but narrow patch will have a low related circumscribing circle index owing to the compact nature of these polygon.
The following is an example of a Python script that uses this tool:
wd = pluginHost.getWorkingDirectory()
inputFile = wd + "polygons.shp" # vector input
outputFile = "" # ignored for vector input
textOutput = "false" # also ignored
zerosAreBackground = "false" # also ignored
args = [inputFile, outputFile, textOutput, zerosAreBackground]
pluginHost.runPlugin("RelatedCircumscribingCircle", args, False)
This is a Groovy script also using this tool:
def wd = pluginHost.getWorkingDirectory()
def inputFile = wd + "polygons.dep" // raster input
def outputFile = wd + "output.dep"
def textOutput = "true"
def zerosAreBackground = "true"
String[] args = [inputFile, outputFile, textOutput, zerosAreBackground]
pluginHost.runPlugin("RelatedCircumscribingCircle", args, False)