ratkowsky.onions {agridat} | R Documentation

## 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.

### 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

    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')
    }

[Package agridat version 1.16 Index]