danlwarren

# Function to rarefy point data in any number of dimensions.  The goal here is to 
# take a large data set and reduce it in size in such a way as to approximately maximize the 
# difference between points.  For instance, if you have 2000 points but suspect a lot of 
# spatial autocorrelation between them, you can pass in your data frame, the names (or indices)
# of the lat/lon columns, and the number 200, and you get back 200 points from your original data 
# set that are chosen to be as different from each other as possible given a randomly chosen
# starting point

# Input is:
#

danlwarren

library(entropy)
library(ggplot2)


olaps <- function(sp1, sp2){
  sp1 <- sp1/sum(sp1)
  sp2 <- sp2/sum(sp2)
  
  plot.table <- data.frame(species = c(rep("sp1", length(sp1)), rep("sp2", length(sp2))),
                           env = c(seq(1:length(sp1)), seq(1:length(sp2))),