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NAMEv.perturb - Random location perturbations of vector points.KEYWORDSvector, geometry, statistics, random, point pattern, level1SYNOPSISv.perturbv.perturb --help v.perturb [-b] input=name [layer=string] output=name [distribution=string] parameters=float[,float,...] [minimum=float] [seed=integer] [--overwrite] [--help] [--verbose] [--quiet] [--ui] Flags:
Parameters:
DESCRIPTIONv.perturb reads a vector map of points and writes the same points but perturbs the eastings and northings by adding either a uniform or normal delta value. Perturbation means that a variating spatial deviation is added to the coordinates.NOTESThe uniform distribution is always centered about zero. The associated parameter is constrained to be positive and specifies the maximum of the distribution; the minimum is the negation of that parameter. Do perturb into a ring around the center, the minimum parameter can be used.Usually, the mean (first parameter) of the normal distribution is zero (i.e., the distribution is centered at zero). The standard deviation (second parameter) is naturally constrained to be positive. Output vector points are not guaranteed to be contained within the current geographic region. EXAMPLESRandom, uniformly distributed selectionTo create a random, uniformly distributed selection of possible new points with a radius of 100,000 map units, use the following command:v.perturb input=comm_colleges output=uniform_perturb parameters=100000Your map should look similar to this figure: Figure: Map showing the actual community college points and uniformly random chosen points. Normal distributed selectionFor a normal distribution with a mean of 5000 and standard deviation of 2000, use the following command:v.perturb input=comm_colleges output=normal_perturb distribution=normal parameters=5000,2000 Figure: Map showing the actual community college points and normally random chosen and colored points. Notice that each point is closer to the original point. Normal distributed selection with a minimum valueIn order to include a minimum value of 500, use the following command:v.perturb input=comm_colleges output=min_perturb distribution=normal parameters=100000,1000 minimum=500 SEE ALSOv.random, v.univarAUTHORJames Darrell McCauleywhen he was at: Agricultural Engineering Purdue University Random number generators originally written in FORTRAN by Wes Peterson and translated to C using f2c. SOURCE CODEAvailable at: v.perturb source code (history)Main index | Vector index | Topics index | Keywords index | Graphical index | Full index © 2003-2021 GRASS Development Team, GRASS GIS 7.8.6 Reference Manual
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