# VfSymLinear (arcpy.sa)

## 插图

 路径距离功能的 VfSymLinear 垂直系数。

## 讨论

VfSymLinear 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。

VfSymLinear 类由两个与 VRMA 相关的线性函数组成，这两个函数关于 VF (y) 轴对称。两条线都在与零系数相关联的 VF 值处截取 y 轴。使用斜率垂直系数参数针对正 VRMA 定义线的斜率，然后将针对负 VRMA 生成一个镜像。

## 语法

VfSymLinear ({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 symmetric 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

VfSymLinear 示例 1（Python 窗口）

``````import arcpy
from arcpy import env
from arcpy.sa import *
env.workspace = "C:/sapyexamples/data"
myVerticalFactor = VfSymLinear(1.0, -90, 90, -0.01111)
outPathDist = PathDistance("source.shp", "costraster", "", "", "", "",
myVerticalFactor)
outPathDist.save("C:/sapyexamples/output/pathdistvfsl")
``````
VfSymLinear 示例 2（独立脚本）

``````# Name: VfSymLinear_Ex_02.py
# Description: Uses the VfSymLinear 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 VfSymLinear Object
zeroFactor = 1.0
lowCutAngle = -90
highCutAngle = 90
slope = -0.01111
myVerticalFactor = VfSymLinear(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/pathdistvfsl2")
``````

5/10/2014