Here is code in R. It requires the rgdal library. If you search around the forum there are some example scripts for calling R from ArcMap. Here is one example form the ESRI scripts page.http://resources.arcgis.com/gallery/file/geoprocessing/details?entryID=F855D6D1-1422-2418-A0B2-643E6...##################################################################
# PROGRAM: RandomFeatureSample.R
# USE: RANDOM SAMPLING OF SPATIAL OBJECTS
# REQUIRES: SP CLASS SpatialDataFrame OBJECT
#
# FUNCTIONS:
# RandSP(x, ns=10, reps=1, replace=FALSE)
#
# ARGUMENTS:
# x SP CLASS SpatialDataFrame OBJECT (POINT, POLYGON, LINE, PIXEL)
# n NUMBER OF RANDOM SAMPLES
# reps NUMBER OF REPLICATES (STRATA)
# replace SAMPLE WITH REPLACEMENT (DEFAULT FALSE)
# ... OPTIONAL ARGUMENTS TO PASS TO sample
#
# VALUE:
# SUBSAMPLE OF SP FEATURECLASS AS SAME SP CLASS
#
# NOTES:
# IF REPLACEMENT IS FALSE FEATURES ARE REMOVED FROM CONSIDERATION IN SUBSEQUENT
# REPS
# THIS MEANS THAT IF TRUE, THAT A FEATURE CAN BE SELECTED MULTIPLE TIMES ACROSS
# REPLICATES. NOT RELEVANT IF REP=1.
#
# EXAMPLES:
# require(rgdal)
# require(sp)
# # READ SHAPEFILE USING RGDAL
# shape <- readOGR(dsn="C:/test", layer="polys", driver="ESRI Shapefile")
#
# # CREATES 4 REPLCATES WITH 5 RANDOM SAMPLES EACH WITHOUT REPLACEMENT
# ssample <- RandSP(shape, n=5, reps=4, replace=FALSE)
#
# # CREATES 1 REPLCATE WITH 10% RANDOM SAMPLE WITHOUT REPLACEMENT
# ssample <- RandSP(shape, n=round(dim(shape)[1]*0.10), digits=0), reps=1, replace=FALSE)
#
# # WRITE RANDOM SAMPLE SHAPEFILE USING RGDAL
# writeOGR(ssample, dsn="C:/test", layer="RandSample", driver="ESRI Shapefile")
#
# # PLOT RANDOM SAMPLES COLORED BY REPLICATE
# spplot(ssample, "REP", col.regions=terrain.colors(n=length(unique(ssample@data$REP))))
#
# REFERENCES:
# B.D. Ripley, 1981. Spatial Statistics, Wiley
#
# CONTACT:
# Jeffrey S. Evans
# Senior Landscape Ecologist
# The Nature Conservancy - Central Science
# Laramie, WY
# (970)672-6766
# jeffrey_evans@tnc.org
##################################################################
RandSP <- function(x, n=10, reps=1, replace=FALSE, ...)
{
if (!require(sp)) stop("sp PACKAGE MISSING")
if (!inherits(x@data, "data.frame")) stop("MUST BE SP SpatialDataFrame OBJECT")
spx <- x
if ( dim(spx)[1] > n ) {
s <- sample(1:nrow(spx@data), n)
results <- spx[s, ]
results@data <- data.frame(results@data, REP=1)
if(replace==FALSE) { spx <- spx[-s, ] }
if(reps > 1) {
for (i in 2:reps ) {
s <- sample(1:nrow(spx@data), n)
ssamp <- spx[s, ]
ssamp@data <- data.frame(ssamp@data, REP=i)
results <- rbind(results, ssamp)
if(replace==FALSE) { spx <- spx[-s, ] }
}
}
}
return( results )
}
