[R-sig-Geo] sample with varying intensity according to local density

[Nicolas Meurisse]

Hi all,

I want to sample locations within a defined area, but also optimize the spatial arrangement of my sample locations in order to:

1.       sample some parts of the area more intensively (e.g. as a function of previous findings intensity, as it could be illustrated by a density map)

2.       sample at regular intervals within each area, as opposed to pure random sampling (e.g. "regular" or "stratified random" as defined in sp package)

Here an example dataset:
n <- 10000
x1  <- matrix(rnorm(n), ncol = 2)
x2  <- matrix(rnorm(n, mean = 3, sd = 1.5), ncol = 2)
x   <- rbind(x1, x2)
# scatterplot with smoothed densities color representation
smoothScatter(x)
# random sampling (not appropriate, as we want an arrangement that optimizes conditions 1 and 2)
points(sample(x[,1],20), sample(x[,2],20), col="red", pch=16)

I would greatly appreciate any insight someone might have as it seems there are lot of potential applications using  such "stratified" sampling.

Many thanks !

Nicolas

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