Yields from treatment for mildew control

Format

A data frame with 38 observations on the following 4 variables.

plot: plot number
trt: treatment factor, 4 levels
block: block factor, 9 levels
yield: grain yield, tons/ha

Details

There were four spray treatments: 0 (none), 1 (early), 2 (late), R (repeated).

Each treatment occurs once between each of the 9 ordered pairs of the other treatments.

The first and last plot are not assigned to a block.

Source

Norman Draper and Irwin Guttman (1980). Incorporating Overlap Effects from Neighboring Units into Response Surface Models. Appl Statist, 29, 128–134. https://doi.org/10.2307/2986297

References

Maria Durban, Christine Hackett, Iain Currie. Blocks, Trend and Interference in Field Trials.

Examples

if (FALSE) { # \dontrun{

library(agridat)
data(jenkyn.mildew)
dat <- jenkyn.mildew

libs(lattice)
bwplot(yield ~ trt, dat, main="jenkyn.mildew", xlab="Treatment")

# Residuals from treatment model show obvious spatial trends
m0 <- lm(yield ~ trt, dat)
xyplot(resid(m0)~plot, dat, ylab="Residual",
       main="jenkyn.mildew - treatment model")

# The blocks explain most of the variation
m1 <- lm(yield ~ trt + block, dat)
xyplot(resid(m1)~plot, dat, ylab="Residual",
       main="jenkyn.mildew - block model")

} # }