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

Description Format Details Source References Examples

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.

Source

Ratkowsky, D. A. (1983). Nonlinear Regression Modeling: A Unified Practical Approach. New York: Marcel Dekker.

References

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

Examples

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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')
}

agridat documentation built on May 2, 2019, 4:01 p.m.