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10
votes
5answers
7k views

How to randomly subset X% of selected points?

What methods are available in ArcGIS 10.2 to randomly subset a selection of points. For example, in the attached screenshot I am interested in keeping 20% of the selected points and deleting the rest....
10
votes
3answers
867 views

How to create random points outside polygons?

The tool Create Random Point is able to generate a certain number of points within polygons. I am wondering, given a bounding box, is there any way that I can generate random points outside those ...
7
votes
3answers
1k views

R - How to sampleRandom() from large raster without NA values

I have a number of vary large rasters which need to be randomly sampled with the return value being a matrix of x, y, and value. The raster package sampleRandom(raster,n, na.rm=TRUE, xy=TRUE) will do ...
5
votes
2answers
128 views

How to randomly select n points within a radius in QGIS?

I have a dataset of 5000 records which I've plotted over an OSM layer using QGIS and I wish to randomly select 50 from within a radius of 2km from a point of my choosing. It is similar I think to ...
5
votes
2answers
78 views

Placing random line segments within polygon?

I would like to generate multiple line segments of a fixed length, a random bearing, and both segment endpoints within the polygon. It's not clear from the example, but it's fine if the segments ...
5
votes
2answers
941 views

How to perform Intersection using ModelBuilder iteration?

I would like to take the intersection of two areas (one randomly generated), and do this n times. I can do it and get one result, but I can't save all the intersection areas to a file at the end. ...
5
votes
1answer
3k views

Creating a subset of points shapefile with minimum distance between points in ArcGIS 10 [duplicate]

I have a sample of ~700 animal locations that I will be using for habitat selection analysis. I am trying to figure out a way to subsample my locations in a way that will maximize my sample size for ...
5
votes
1answer
2k views

Is there a source for free CSV files with geo data and other desired fields? [closed]

I'm writing some software components that process geospatial data. The input data is a CSV with general columns (e.g. name) and geo columns (e.g. city, lat or zip). I would like to test these ...
4
votes
1answer
97 views

How to insert random points with weight?

I have a polygon shp divided in 5 regions. I want to fill it with 1000 random points but not to be so random :). I want 300 points to fill one region 100 another...for the moment the one tough ...
4
votes
2answers
680 views

Randomly sampling points in R with minimum distance constraint

I'm trying to randomly select a number of points within my data frame (example data below) with a constraint that the minimum distance between the selected point must be greater than a certain ...
4
votes
1answer
551 views

Is there any random data generator supporting geometry in PostGIS?

I found few random data generators for PostgreSQL (such as this one), but none supporting PostGIS geometry type, other than point. Making points would be quite easy, but for lines with multiple nodes ...
4
votes
1answer
62 views

Stratified Random Sampling Tool

Is there a way to produce a certain amount of random points over different classes in a raster in QGIS? I have extensions such as GRASS or GDAL, ...
4
votes
2answers
262 views

How to randomly move points?

I have a feature class with a large amount of points. My purpose is to randomly move these points to see what happens as a result. Are there specific tools or Python programming methods to accomplish ...
4
votes
1answer
72 views

How to randomly position coordinates within a containing feature in QGIS?

I have geocoded address data, and I am wishing to randomly position it within the census tracts that they are in to obfuscate... So the points are still within the feature but randomly move around so ...
3
votes
2answers
947 views

Script or model to create random points having multiple minimum distances within a polygon

Given: A single part polygon, total number of points to place inside that polygon, and table specifying the size of each subset (number of subsets n >= 1) of that total number of points and each ...
3
votes
2answers
65 views

Knowing if there is correlation between roads and observations in ArcMap?

I am using ArcMap 10.3.1. I am trying to find out whether some observations have been made randomly throughout a landscape, or they are biased towards the location of roads and paths. I have a ...
3
votes
2answers
925 views

Using arcgis.rand() with variables from code block of Calculate Value tool?

Within a larger ArcGIS ModelBuilder model I am trying to populate a field in an attribute table with a random number, using Calculate Value. The overall distribution of random numbers needs to follow ...
3
votes
1answer
420 views

How to create randomly points within polygons for each row of a dataframe matching a Polygon ID with R

My question is similar to this post, but because there are no "perfect" answer and above all no reproducible example I open this question. I have a "SpatialPolygonsDataFrame" and a data frame. Both ...
3
votes
1answer
172 views

Is the QGIS “Random selection within subset” selecting spatially random or randomly from the attribute table?

I am trying to figure out exactly what is being randomly selected. I have a layer of road segments and I would like it to select a road segment at random within a neighborhood (the subset). This would ...
3
votes
2answers
386 views

Step by step contour creation algorithm

I do seismic processing, and recently have been moving into doing contours. I have a question on the exact way this is done. I have watered down my problem so that I can understand from 'first ...
3
votes
1answer
549 views

Convert polygons to a number of randomly located points based on polygon size

ArcMap 10.1 on a PC. Working with a large shapefile with ~50,000 poygons with a wide range of size from 1,000+m. to <1m. I would like to convert these polygons into points so I can do some analysis ...
3
votes
1answer
52 views

creating unique sets randomly distributed values for many defined areas…in a raster.

I have a large approximately circular study area comprised of 5000+ polygons which represent forest parcels. For each of these polygons I have up to 4 different species. These species occur in ...
3
votes
0answers
28 views

Sample Design for Kriging

I am taking soil samples on an agricultural plot and will be using the results as input to create a semivariogram for kriging in ArcGIS. This plot features raised planting beds in which the test crop ...
2
votes
1answer
262 views

Using Python to select random location from shapefile?

I have multiple shapefiles with bars names and location attributes and I want to create a script which asks the user for the area or shapefile name where they want to go and then prints a random ...
2
votes
4answers
1k views

How to create random point in according polygon for each dataset entry in a list (with R)

I have an area divided into polygons, and a dataset of observations which has a common field with the polygon layer. I now would like to generate a random point for each dataset entry within the ...
2
votes
2answers
165 views

Creating random points using QGIS using Random points tool?

I have a polygon layer that has plot layouts of an area. I want to create a random point on each polygon. I tried to use the Random points tool (Vector->Research Tool->Random Points) to create the ...
2
votes
1answer
89 views

Using search and update cursors for random number generation

I am having some trouble getting a searchcursor to return a value for each record. The purpose of my code is to scan through a list of records in a field (FieldA) and based on those values populate a ...
2
votes
1answer
54 views

Randomly distributed cases according to census data

I'd like to randomly place a point within a geographic boundary with the caveat that I would like to use census data so that points are randomly placed according to population density (i.e. more ...
2
votes
1answer
389 views

Stratified Random Sampling by ID in QGIS?

I've been playing around with the Random Points tool in QGIS to realize stratified random sampling, but I'm running into a problem where I want my strata to be based on a polygon ID, not each ...
2
votes
2answers
113 views

How to select 200 random points within a 100m radius in Postgis

I'm currently learning to use PostgreSQL and PostGIS. I would like to know how to write the SQL that would allow me to select 200 random points within a radius of 500m from a user defined centre point....
2
votes
1answer
115 views

What is CID field created by Create Random points?

In ArcGIS the result of Create Random Points tool when using a feature class to constrain the extents has an attribute called CID. What do the values in this field represent?
2
votes
2answers
290 views

Creating Random Points that respect minimal distance across features / strata using ArcGIS for Desktop?

I have a shapefile with multiple polygons in which I want to distribute random points. Each polygon should contain exactly one point. The minimal distance between the random points should be 200m. ...
2
votes
0answers
20 views

How to generate random points from classified raster layer?

I need to generate random points using a raster layer, which is classified into 5 classes of TPI (terrain position index). This should be a stratified random sampling design, with an equal amount of ...
2
votes
1answer
596 views

Create random points in ArcGIS on a polyline in a polygon

I am trying to create 100 random points, 1 within 500m of 100 points I already have. I have created a buffer and can easily create 1 random point in each, but now I want those points to lie on a ...
2
votes
1answer
539 views

How do I select random points within each land-cover class? [closed]

I have a MODIS file and I want to Select random points within each land cover class Extract values of rasters to the sample points. Export attribute table Could you please tell me what steps I ...
1
vote
2answers
262 views

Random Value Generator

I have a python code where I am trying to assign a unique, random value to every row. I have tried: maxvalue = int(arcpy.GetCount_management(shape).getOutput(0)) + 10000 for row in arcpy.SearchCursor(...
1
vote
2answers
204 views

How to generate random points from FIDs using ArcPy or ArcGIS Field Calculator?

I'm trying to generate a shapefile of random points using FID from the attribute table. My attribute table has 800,000 features and I only need a sample of 240. Is there a way to do it in arcpy or in ...
1
vote
1answer
356 views

Sorting points with QGIS

I have a very good idea of what I would like to do but I really do not know if it is possible with QGIS. I have points that each one corresponds to a group size and I would like to use GIS to sort ...
1
vote
1answer
233 views

arcpy geometry difference method fails randomly, not reproducible

Has anyone used the arcpy geometry difference operator and seen unexplained errors like what I describe below? This is a weird one. I have a script that calculates wave fetch distance in the ocean ...
1
vote
3answers
39 views

ArcMap Random Points Minimum Distance Field not able to use units

I would like to create random points with a minimum distance based on an attribute field (polygons with a larger area need random points with more space between them). In theory this can be done. ...
1
vote
1answer
98 views

creating a random gdal raster with random predefined values

So far I have developed the below code but for some reason it only works for say one class of landuse instead of two. Would you please tell me where I have gone wrong? Thanks so much import os, numpy,...
1
vote
1answer
115 views

Python Code for generating random points not working!

I am trying to create some code to generate 10 random points within a vector layer's districts: layer=iface.activeLayer() import ogr import sys import random from shapely import wkb, geometry Moz_no=...
1
vote
3answers
4k views

Generate random location within specified distance of a given point

In a simulation (not using any GIS), I need to generate a random location that is within a specified distance of a given location. I found a very helpful post here on this exact topic: How to ...
1
vote
1answer
129 views

Set certain amount of pixels to 1 inside of a polygon (GRASS)

I have a rather coarse vector map with polygons and want to calculate a (sufficiently) finer raster map defined by spatial extension and resolution. Every polygon of the vector map has a value ...
1
vote
1answer
29 views

Random Selection using Select By Attributes tool in ArcMap?

How I can make a SQL syntax to generate "RANDOM SELECTION" in Select by attributes tool in ArcMap?. E.g. We have two kind of sample: Quantitative an Qualitative data. Quantitative (seven cases): 1,...
1
vote
0answers
68 views

Random forest in ecognition

I'm using eCognition to mapping roof materials from SPOT 6 image. I have used nearest neighbour classification but the result is not so good. I'm trying to apply a random forest classifier if it is ...
1
vote
0answers
185 views

Creating multipart polygons with ArcPy? Dissolve Failure?

I need the functionality of the editor > merge command for use in a python script tool. I realize this function is not directly accessible through ArcPy, but I am hoping someone can help with a work ...
1
vote
0answers
65 views

Creating random points using QGIS?

Has anyone else had any issues using the random points tool in QGIS? When I try using it I'm selecting the option to use a value input field. The tool starts but then freezes once it gets to the 10% ...
1
vote
0answers
35 views

Random points by percent coverage

Yes, I know the math behind this is simple, but I'm looking for a way to automate the process. In ArcGIS 10.2.2. is it possible with the Create Random Points data management tool to generate a set of ...
1
vote
1answer
90 views

How to create landscape resistance map using path level spatial randomisation in QGIS?

I need to create a landscape resistance map based on path level spatial randomisation, as I have read in some research papers. Are there tools for this? I need to randomly shift and rotate the the ...