Barley Seeding Rate Data
The seedrates data frame has 5 rows and 2 columns on
the effect of seeding rate of barley on yield.
seedrates
This data frame contains the following columns:
the seeding rate
the number of grain per head of barley
McLeod, C.C. 1982. Effect of rates of seeding on barley grown for grain. New Zealand Journal of Agriculture 10: 133-136.
Maindonald J H 1992. Statistical design, analysis and presentation issues. New Zealand Journal of Agricultural Research 35: 121-141.
plot(grain~rate,data=seedrates,xlim=c(50,180),ylim=c(15.5,22),axes=FALSE) new.df<-data.frame(rate=(2:8)*25) seedrates.lm1<-lm(grain~rate,data=seedrates) seedrates.lm2<-lm(grain~rate+I(rate^2),data=seedrates) hat1<-predict(seedrates.lm1,newdata=new.df,interval="confidence") hat2<-predict(seedrates.lm2,newdata=new.df,interval="confidence") axis(1,at=new.df$rate); axis(2); box() z1<-spline(new.df$rate, hat1[,"fit"]); z2<-spline(new.df$rate, hat2[,"fit"]) rate<-new.df$rate; lines(z1$x,z1$y) lines(spline(rate,hat1[,"lwr"]),lty=1,col=3) lines(spline(rate,hat1[,"upr"]),lty=1,col=3) lines(z2$x,z2$y,lty=4) lines(spline(rate,hat2[,"lwr"]),lty=4,col=3) lines(spline(rate,hat2[,"upr"]),lty=4,col=3)
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