Ln (Image Analyst)

This ArcGIS 2.7 documentation has been archived and is no longer updated. Content and links may be outdated. See the latest documentation.

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.

Syntax

Ln(in_raster_or_constant)
ParameterExplanationData 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

Related topics