Description Format Details Source References Examples

Onion yields for different densities at two locations

This data frame contains the following columns:

- density
planting density (plants per square meter)

- yield
yield (g / plant)

- loc
location, Purnong Landing or Virginia

Spanish white onions.

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

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

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 | ```
## Not run:
library(agridat)
data(ratkowsky.onions)
dat <- ratkowsky.onions
# Model inverse yield as a quadratic. Could be better...
libs(lattice)
dat <- transform(dat, iyield = 1/yield)
m1 <- lm(iyield ~ I(density^2)*loc, dat)
dat$pred <- predict(m1)
libs(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')
## End(Not run)
``` |

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