Ln (Image Analyst)

Available with Spatial Analyst license.

Available with Image Analyst license.

Summary

Calculates the natural logarithm (base e) of cells in a raster.

Illustration

Ln illustration
OutRas = Ln(InRas1)

Usage

  • The input can be of integer or float type.

    You can review some results for floating-point input values in the examples of output values from the Logarithmic tools.

  • Input values that are 0 or negative will be NoData in the output raster.

  • The output raster from this tool is always floating-point type, regardless of the input value type.

  • If the input is a multiband raster, the output will be a multiband raster. The tool will perform the operation on each band in the input.

  • The natural logarithm (Ln) is the most commonly used logarithmic function.

  • In ArcPy, if the input is a multidimensional raster, all slices from all variables will be processed, and the output will be a multidimensional raster.

Parameters

LabelExplanationData Type
Input raster or constant value

Input values for which to find the natural logarithm (Ln).

To use a number as an input for this parameter, the cell size and extent must first be set in the environment.

Raster Layer; Constant

Return Value

LabelExplanationData Type
Output raster

The output raster.

The cell values are the base e (natural) logarithm of the input values.

Raster

Ln(in_raster_or_constant)
NameExplanationData Type
in_raster_or_constant

Input values for which to find the natural logarithm (Ln).

To use a number as an input for this parameter, the cell size and extent must first be set in the environment.

Raster Layer; Constant

Return Value

NameExplanationData Type
out_raster

The output raster.

The cell values are the base e (natural) logarithm of the input values.

Raster

Code sample

Ln example 1 (Python window)

This example calculates the natural logarithm (base e) of the input raster values.

import arcpy
from arcpy import env
from arcpy.ia import *
env.workspace = "C:/iapyexamples/data"
outLn = Ln("elevation")
outLn.save("C:/iapyexamples/output/outln2")
Ln example 2 (stand-alone script)

This example calculates the natural logarithm (base e) of the input raster values.

# Name: Ln_Ex_02.py
# Description: Calculates natural logarithm (base e) of pixels in a raster
# Requirements: Image Analyst Extension

# Import system modules
import arcpy
from arcpy import env
from arcpy.ia import *

# Set environment settings
env.workspace = "C:/iapyexamples/data"

# Set local variables
inRaster = "elevation"

# Check out the ArcGIS Image Analyst extension license
arcpy.CheckOutExtension("ImageAnalyst")

# Execute Ln
outLn = Ln(inRaster)

# Save the output 
outLn.save("C:/iapyexamples/output/outln")

Licensing information

  • Basic: Requires Image Analyst or Spatial Analyst
  • Standard: Requires Image Analyst or Spatial Analyst
  • Advanced: Requires Image Analyst or Spatial Analyst

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