Barley Seeding Rate Data

Description

The seedrates data frame has 5 rows and 2 columns on the effect of seeding rate of barley on yield.

Usage

seedrates

Format

This data frame contains the following columns:

rate

the seeding rate

grain

the number of grain per head of barley

Source

McLeod, C.C. 1982. Effect of rates of seeding on barley grown for grain. New Zealand Journal of Agriculture 10: 133-136.

References

Maindonald J H 1992. Statistical design, analysis and presentation issues. New Zealand Journal of Agricultural Research 35: 121-141.

Examples

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)