x<-c(103,31,115,76,40,101,69,75) y<-c(22,105,49,34,79,85,96,90) y<-150-y angle<-c() for(i in 1:8) angle<-c(angle,atan2(y[i]-75,x[i]-75)) angle<-180*angle/3.1415 angle2<-angle angle[angle2>=-180 & angle2<=90] <- 90 - angle[angle2>=-180 & angle2<=90] angle[angle2>90 & angle2<=180] <- 450 - angle[angle2>90 & angle2<=180] temp<-"" for(j in angle) for(i in 1:length(LETTERS)) { intmin<-(i-1)*360/length(LETTERS) intmax<-i*360/length(LETTERS) if(j>=intmin & j<=intmax) temp<-paste(temp,LETTERS[i],sep="") } temp