# Ln (Spatial Analyst)

## Summary

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

## 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

 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

`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.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