# VfLinear

## Summary

Defines the relationship between the vertical cost factor and the vertical relative moving angle through a linear function.

## Discussion

This object is used in the Distance Accumulation and Distance Allocation Spatial Analyst tools, as well as the Path Distance, Path Distance Allocation, and Path Distance Back Link Legacy Distance tools.

The vertical factor (VF) object defines the relationship between the vertical cost factor and the vertical relative moving angle (VRMA).

VF defines the vertical difficulty encountered in moving from one cell to the next.

VRMA identifies the slope angle between the FROM or processing cell and the TO cell.

The VFs are determined by a straight line in the VRMA-VF coordinate system. The line intercepts the y-axis, equitable to the VF factor, at the value associated with the zeroFactor. The slope of the line can be specified using the slope argument.

## Syntax

`VfLinear ({zeroFactor}, {lowCutAngle}, {highCutAngle}, {slope})`
 Parameter Explanation Data Type zeroFactor The zeroFactor will be used to position the y-intercept of the linear function.(The default value is 1.0) Double lowCutAngle The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity.(The default value is -90.0) Double highCutAngle The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity.(The default value is 90.0) Double slope Identifies the slope of the straight line in the VRMA-VF coordinate system. Slope is specified as the rise/run. For example, a 30-degree slope is 1/30, specified as 0.03333 (rise/run: 1 VF on the y axis / 30 degrees on the x axis); a 90-degree slope as 0.011111.(The default value is 0.011111) Double

## Properties

 Property Explanation Data Type zeroFactor(Read and Write) The zeroFactor is used to position the y-intercept for the vertical factor class. Double lowCutAngle(Read and Write) The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity. Double highCutAngle(Read and Write) The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity. Double slope(Read and Write) Identifies the slope of the straight line in the VRMA-VF coordinate system. Slope is specified as the rise over the run. For example, a 30-degree slope is 1/30, specified as 0.03333 (rise/run: 1 VF on the y axis / 30 degrees on the x axis); a 90-degree slope as 0.011111. Double

## Code sample

VfLinear example 1 (Python window)

Demonstrates how to create a VfLinear class and use it in the DistanceAccumulation tool within the Python window.

``````import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
myVerticalFactor = VfLinear(1.0, -90.0, 90.0, 0.01111)
outDistAccum = DistanceAccumulation("Source.shp", "", "elev.tif",
"cost.tif", "elev.tif",
myVerticalFactor)
outDistAccum.save("C:/sapyexamples/output/distAccumVfL.tif")``````
VfLinear example 2 (stand-alone script)

Performs a DistanceAccumulation analysis using the VfLinear class.

``````# Name: VfLinear_Ex_02.py
# Description: Uses the VfLinear object to run the
#              DistanceAccumulation tool
# 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
inSourceData = "source.shp"
inCostRaster = "costraster.tif"
inElevation = "elev.tif"

# Create the VfLinear Object
zeroFactor = 1.0
lowCutAngle = -90
highCutAngle = 90
slope = 0.01111
myVerticalFactor = VfLinear(zeroFactor, lowCutAngle, highCutAngle, slope)

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

# Execute PathDistance
outDistAccum = DistanceAccumulation(inSourceData, "", inElevation,
inCostRaster, inElevation,
myVerticalFactor)

# Save the output
outDistAccum.save("C:/sapyexamples/output/distaccumvfL2.tif")``````