wheatdata {SpATS}

Wheat yield in South Australia

Description

A randomized complete block experiment of wheat in South Australia (Gilmour et al., 1997).

Usage

data("wheatdata")

Format

A data frame with 330 observations on the following 7 variables

yield

yield, numeric

geno

wheat variety, a factor with 107 levels

rep

replicate factor, 3 levels

row

row position, numeric

col

column position, a numeric vector

rowcode

a factor with 2 levels. This factor is related to the way the trial and the plots were sown (see Details).

colcode

a factor with 3 levels. This factor is related to the way the plots were trimmed to an assumed equal length before harvest (see Details).

Details

A near complete block design experiment. In this experiment, a total of 107 varieties were sown in 3 replicates in a near complete block design (3 varieties were sown twice in each replicate). Each replicate consisted of 5 columns and 22 rows. Accordingly, the field consists on 15 columns and 22 rows (i.e. a total of 330 plots or observations). Trimming was done by spraying the wheat with herbicide. The sprayer travelled in a serpentine pattern up and down columns. More specifically, the plots were trimmed according to four possible combinations: up/down, down/down, down/up, and up/up. The colcode factor describe this 4-phase sequence. With respect to the way the trial was sown, the procedure was done in a serpentine manner with a planter that seeded three rows at a time (Left, Middle, Right). This fact led to a systematic effect on the yield due to sowing. The variable rowcode describes the position of each plot in the triplet (Left, Middle, Right). Level 1 was used for the middle plot, and 2 for those on the right or on the left of the triplet (see Gilmour et al. (1997) for more details).

Source

Gilmour, A.R., Cullis, B.R., and Verbyla, A.P. (1997). Accounting for Natural and Extraneous Variation in the Analysis of Field Experiments. Journal of Agricultural, Biological, and Environmental Statistics, 2, 269 - 293.

Kevin Wright (2015). agridat: Agricultural datasets. R package version 1.12. http://CRAN.R-project.org/package=agridat

Examples

library(SpATS)
data(wheatdata)
summary(wheatdata)