# VfLinear (arcpy.sa)

## 插图

 路径距离功能的 VfLinear 垂直系数。

## 讨论

VfLinear 对象用于 Spatial Analyst 工具路径距离路径距离分配路径距离回溯链接

VF 用于定义从一个像元移至下一像元的垂直阻力。

VRMA 用于确定“起始”像元或处理像元与“终止”像元之间的坡度角。

VF 由 VRMA-VF 坐标系中的一条直线确定。这条线在 y 轴（表示 VF 系数）上与零系数相关联的值处进行截取。线的斜率可以通过斜率参数指定。

## 语法

VfLinear ({zeroFactor}, {lowCutAngle}, {highCutAngle}, {slope})
 参数 说明 数据类型 zeroFactor The zeroFactor will be used to position the y-intercept of the linear function. (默认值为 1.0) Double lowCutAngle The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity. (默认值为 -90.0) Double highCutAngle The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity. (默认值为 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. (默认值为 0.011111) Double

## 属性

 属性 说明 数据类型 zeroFactor(读写) The zeroFactor is used to position the y-intercept for the vertical factor class. Double lowCutAngle(读写) The VRMA degree defining the lower threshold, below which (less than) the VFs are set to infinity. Double highCutAngle(读写) The VRMA degree defining the upper threshold, beyond which (larger than) the VFs are set to infinity. Double slope(读写) 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

## 代码实例

VfLinear 示例 1（Python 窗口）

``````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)
outPathDist =  PathDistance("source.shp", "costraster", "", "", "", "",
myVerticalFactor)
outPathDist.save("C:/sapyexamples/output/pastdistvfl")
``````
VfLinear 示例 2（独立脚本）

``````# Name: VfLinear_Ex_02.py
# Description: Uses the VfLinear object to execute the PathDistance 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"

# 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
outPathDist =  PathDistance(inSourceData, inCostRaster, "", "", "", "",
myVerticalFactor)

# Save the output
outPathDist.save("C:/sapyexamples/output/pastdistvfl2")
``````

5/10/2014