Ln (Spatial 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.

  • See Analysis environments and Spatial Analyst for additional details on the geoprocessing environments that apply to this tool.

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.sa import *
env.workspace = "C:/sapyexamples/data"
outLn = Ln("elevation")
outLn.save("C:/sapyexamples/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 cells in a raster
# Requirements: Spatial Analyst Extension

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

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

# Set local variables
inRaster = "elevation"

# Execute Ln
outLn = Ln(inRaster)

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

Licensing information

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

Related topics