agridat (version 1.16)

ratkowsky.onions: Onion yields for different densities at two locations

Description

Onion yields for different densities at two locations

Format

This data frame contains the following columns:

density

planting density (plants per square meter)

yield

yield (g / plant)

loc

location, Purnong Landing or Virginia

Details

Spanish white onions.

References

Ruppert, D., Wand, M.P. and Carroll, R.J. (2003). Semiparametric Regression. Cambridge University Press. http://stat.tamu.edu/~carroll/semiregbook/

Examples

# NOT RUN {
data(ratkowsky.onions)
dat <- ratkowsky.onions

# Model inverse yield as a quadratic.  Could be better...
require(lattice)
dat <- transform(dat, iyield = 1/yield)
m1 <- lm(iyield ~ I(density^2)*loc, dat)
dat$pred <- predict(m1)

if(require(latticeExtra)) {
  foo <- xyplot(iyield ~ density, data=dat, group=loc, auto.key=TRUE,
                 main="ratkowski.onions",ylab="Inverse yield")
  foo + xyplot(pred ~ density, data=dat, group=loc, type='l')
}

# }