#resampling 
#open csv file
dat<-read.csv(file.choose())
#average of 1000x by grid cell
riqumedia<-c()
#general loop, second number is maximum value of ID
for(i in 1:279){
#select data of same ID
  testx1<-subset(dat,ID==i,drop=FALSE)
#convert to vector
  avect<-as.vector(testx1[,1])
#create a empity vector
num1<-c()
  for(y in 1:1000){
#sampling inside in one ID
amostra<-c(sample(avect,150,replace=FALSE,prob=NULL))
#nuber of species by sample
n.unique <- function(amostra) {length(unique(amostra))}
num1[y]<-n.unique(amostra)}
#average of richness
riqumedia[i]<-c(mean(num1))}
testy<-as.matrix(riqumedia)
write.csv(testy,file.choose())