Random point generation?

EmmaYoung

Hi-

I have a raster that is classified into 5 different pixel values, and I want to generate 30 random points within each of those pixel classes (for a total of 150 points). I know there is a random point generation tool, but I don't think you can use it to generate points by pixel value? Does anyone know if there is a way to do this in ArcGIS? I've been trying to use IDL, but I've run into problems and so I'm looking for alternatives. Thanks so much.

Cheers,
Emma

JeffreyEvans

Here is a simple R solution.

require(raster)
require(sp)
require(rgdal)

n=30 # NUMBER OF RANDOM SAMPLES PER CLASS

# READ RASTER (NOT RUN) 
#r <- raster("C:/mydata/myraster.img")

# CREATE EXAMPLE DATA WITH 5 CLASSES
r <- raster(ncol=100,nrow=100)
  r[] <- round(runif(100*100, 1,5),digits=0)

# CREATE STRATIFIED RANDOM SAMPLE WITH n SAMPLES PER STRATA (CLASS)  
rs <- sampleStratified(r, size=n, na.rm=TRUE, sp=TRUE) 

# PLOT AND COLOR POINTS BASED ON CLASS
plot(r)
  points(rs, col=rs$layer, pch=19)

# WRITE SHAPEFILE WITH RANDOM POINTS 
writeOGR(rs, "C:/mydata", "RandSamp", driver="ESRI Shapefile")