#SPOT CHECK 1750-1970 CORRELATIONS

  #(i) series must cover at least the interval 1750 to 1970, 
  #(ii) correlation between individual cores for a given site must be 0.50 for this period,

	source("http://www.climateaudit.org/scripts/utilities.treering.txt")

   rbar_mann=function(id) {	
	tree=make.rwl(id) #downloads rwl data from ITRDB
	recon<-collate(tree) ;   M<-ncol(recon)  #makes into time series
	temp=(time(recon)>=1750)&(time(recon)<=1970)
	recon=ts(recon[temp,],start=max(1750,tsp(recon)[1]) ) #limits to 1750-1970
 	corry<-cor(recon,use="pairwise.complete.obs")
	diag(corry)=NA	
	rbar_mann=mean(corry,na.rm=T)
	rbar_mann
	}

	test=rbar_mann("cana159");test  #] 0.3211091
	test=rbar_mann("cana158");test  #0.2278701