Dear all, I am carrying out some species distribution modelling based on a database of species occurrence records of a single tree species, encompassing the entire European continent. The records are primarily historical and heavily biased towards western, northern Europe. A few of the counts of records by country are shown below to illustrate.
CHE 12 CZE 1 DEN 6 DEU 1742 DNK 12 ESP 237 FIN 1 FRA 6536 GBR 3294 GEO 39 GRC 47 HUN 2 I am very new to R and I'm trying to find a way to subsample in order to obtain a more spatially balanced sample of 300 records, from a total of 16794. I have looked at some packages, e.g. sp, spcosa, spsurvey, spdep, have searched the manuals and searched for similar examples. I have also tried to stratify the data but can't find a stratum which reduces the impact of the bias. I also have a field containing inclusion probabilities for each record, based on country. I just can't seem to work out how best to perform sampling to reduce the effect of geopolitical bias. Any advice, for an R novice, would be very gratefully received. Thanks, Claire _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
