DAAG (version 0.37)

seedrates: 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

data(seedrates)

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

data(seedrates)
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)