TfLogisticGrowth

Summary

Defines a Logistic Growth transformation function which is determined from the minimum, maximum, and y intercept percent shape–controlling parameters as well as the lower and upper threshold that identify the range within which to apply the function.

Learn more about how the parameters affect this transformation function

Discussion

The tool that uses the TfLogisticGrowth object is Rescale by Function.

The function values range from 0 to 100, which are then transformed to the evaluation scale.

If the minimum parameter is set greater than the lowerThreshold, or the maximum parameter is set less than the upperThreshold, the function curve will increase at a faster rate. If the minimum parameter is set less than the lowerThreshold, or the maximum parameter is set greater than the upperThreshold, the function curve will increase at a slower rate.

Syntax

TfLogisticGrowth({minimum}, {maximum}, {yInterceptPercent}, {lowerThreshold}, {valueBelowThreshold}, {upperThreshold}, {valueAboveThreshold})

Name	Explanation	Data type
minimum (Optional)	The starting point for the `LogisticGrowth` transformation function. The minimum must be less than the maximum. The default value is None.	Double
maximum (Optional)	The ending point for the `LogisticGrowth` transformation function. The minimum must be less than the maximum. The default value is None.	Double
yInterceptPercent (Optional)	Determines the value range in the increasing portion of the logistic growth curve. The smaller the `yInterceptPercent`, the smaller the input value range will be in the growth section of the curve; however, the preference for the values will increase at a faster rate. A smaller `yInterceptPercent` results in a more pronounced logistic growth curve. The `yInterceptPercent` must be between 0 and 50. The default value is 1.0.	Double
lowerThreshold (Optional)	Defines the starting value at which to begin applying the specified transformation function. The input value corresponding to the `lowerThreshold` is assigned to the `fromScale` evaluation scale value on the output raster. Input values below the `lowerThreshold` are assigned to the `valueBelowThreshold` and are not considered in the function value range. The `lowerThreshold` must be less than the `upperThreshold`. The default value is None.	Double
valueBelowThreshold (Optional)	A value to assign output cell locations with input values below the `lowerThreshold`. The value for `valueBelowThreshold` can be float, integer, or NoData. In the tool dialog box, no quotation marks are used around NoData; however, quotation marks are required around "NoData" when scripting. The default value is None.	Variant
upperThreshold (Optional)	Defines the ending value at which to stop applying the specified transformation function. The input value corresponding to the `upperThreshold` is assigned to the `toScale` evaluation scale value on the output raster. Input values above the `upperThreshold` are assigned to the `valueAboveThreshold` and are not considered in the function value range. The `lowerThreshold` must be less than the `upperThreshold`. The default value is None.	Double
valueAboveThreshold (Optional)	A value to assign output cell locations with input values above the `upperThreshold`. The value for `valueAboveThreshold` can be float, integer, or NoData. In the tool dialog box, no quotation marks are used around NoData; however, quotation marks are required around "NoData" when scripting. The default value is None.	Variant

Properties

Name	Explanation	Data type
minimum (Read and Write)	The value of the `minimum` of the transformation function which defines the starting point for the function.	Double
maximum (Read and Write)	The value of the `maximum` of the transformation function which defines the ending point for the function.	Double
yInterceptPercent (Read and Write)	The value of the `yInterceptPercent` for the transformation function which determines the value range that will be in the increasing portion of the logistic growth curve.	Double
lowerThreshold (Read and Write)	The value of the `lowerThreshold` for the transformation function which defines the starting value at which to begin applying the specified transformation function.	Double
valueBelowThreshold (Read and Write)	The value that will be assigned to the output cells whose input values are below the `lowerThreshold`.	Variant
upperThreshold (Read and Write)	The value of the `upperThreshold` for the transformation function which defines the ending value at which to stop applying the specified function.	Double
valueAboveThreshold (Read and Write)	The value that will be assigned to the output cells whose input values are above the `upperThreshold`.	Variant

Code sample

Transformation function LogisticGrowth example 1 (Python window)

Demonstrates how to create a TfLogisticGrowth class and use it in the RescaleByFunction tool within the Python window.

import arcpy
from arcpy.sa import *
from arcpy import env
env.workspace = "c:/sapyexamples/data"
outRescale = RescaleByFunction("biomass", TfLogisticGrowth(30, 412000, 15, "#", "#", "#", "#"), 1, 10)
outRescale.save("c:/sapyexamples/rescaletflg1")

Transformation function LogisticGrowth example 2 (stand-alone script)

Demonstrates how to transform the input data with the RescaleByFunction tool using the TfLogisticGrowth class.