cor.demo <-
function() {
par(mfrow=c(1,1))
plot(0,0,xlim=c(0,1),col="white",ylim=c(0,1),xlab="x",ylab="y",main="click plot to add points then click END below to stop demo",cex.main=0.9)
rect(-1,.9,.2,2,col="white"); text(0.1,0.95,"r2 = ")
rect(0.55,.9,2,2,col="white"); text(0.8,0.95,"r2 (without red dot) = ")
rect(0,0,.1,.05,col="red"); text(0.05,.025,"END",cex=0.8)
x <- c(); y <- c()
r.old <- 0
keep.going <- 1
while (keep.going==1) {
new.point <- unlist(locator(1))
if( new.point[1] > .1 | new.point[2] > .05 ) {
points(x,y,pch=20,cex=2,col="black")
points(new.point[1],new.point[2],pch=20,cex=2,col="red")
x <- c(x,new.point[1]); y <- c(y,new.point[2])
r <- round(cor(x,y),digits=2)
rect(-1,.9,.2,2,col="white")
text(0.075,1,paste("r =",r))
text(0.075,0.95,paste("r2 =",r^2))
if(length(x)>2) {
rect(0.55,.9,2,2,col="white");
text(0.8,1,paste("r (without red dot) =",round(r.old,digits=2)))
text(0.8,0.95,paste("r2 (without red dot) =",round(r.old^2,digits=2))) }
r.old <- r
} else { keep.going <- 0 }
}
}
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