Ln (Image Analyst)

Available with Spatial Analyst license.

Summary

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

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.

• If the input is multidimensional raster data, all slices from all variables will be processed. The output will be a multidimensional raster in CRF format.

Parameters

Dialog

Label	Explanation	Data 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

Label	Explanation	Data Type
Output raster	The output raster. The cell values are the base e (natural) logarithm of the input values.	Raster

Python

Ln(in_raster_or_constant)

Name	Explanation	Data 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

Name	Explanation	Data 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")

Environments

Auto Commit, Cell Size, Cell Size Projection Method, Current Workspace, Extent, Geographic Transformations, Mask, Output CONFIG Keyword, Output Coordinate System, Scratch Workspace, Snap Raster, Tile Size