agridat (version 1.12)

mercer.wheat.uniformity: Mercer and Hall's uniformity trial of wheat in 1910

Description

Uniformity trial of wheat in 1910

Format

A data frame with 500 observations on the following 4 variables.

row

row, 1-20

col

column, 1-25

grain

grain yield, pounds

straw

straw yield, pounds

Details

The wheat crop was grown in the summer of 1910 at Rothamsted Experiment Station (Harpenden, Hertfordshire, England). In the Great Knott, a seemingly uniform area of 1 acre was harvested in separate plots, each 1/500th acre in size. The grain and straw from each plot was weighed separately.

Row 1 is the south edge, row 20 is the north. Column 1 is the west edge. The dimensions of each plot were approximately 3.2 meters by 2.5 meters.

D. G. Rossiter (2014) uses this data for an extensive data analysis tutorial.

References

D. G. Rossiter (2014). Tutorial: Using the R Environment for Statistical Computing An example with the Mercer & Hall wheat yield dataset.

The 'spdep' package includes the grain yields (only) and spatial positions of plot centres in its example dataset 'wheat'.

Examples

# NOT RUN {
data(mercer.wheat.uniformity)
dat <- mercer.wheat.uniformity

require('lattice')
desplot(grain ~ col*row, dat, main="mercer.wheat.uniformity - grain yield")

xyplot(straw ~ grain, data=dat, type=c('p','r'), main="mercer.wheat.uniformity - regression")

# require(hexbin)
# hexbinplot(straw ~ grain, data=dat)

require(sp)
require(gstat)
plot.wid <- 2.5
plot.len <- 3.2
nr <- length(unique(dat$row))
nc <- length(unique(dat$col))

xy <- expand.grid(x = seq(plot.wid/2, by=plot.wid, length=nc),
y = seq(plot.len/2, by=plot.len, length=nr))
dat.sp <- dat
coordinates(dat.sp) <- xy

# }
# NOT RUN {
# heatmap
spplot(dat.sp, zcol = "grain", cuts=8,
       cex = 1.6,
       col.regions =  bpy.colors(8),
       main = "Grain yield", key.space = "right")

# variogram
vg <- variogram(grain ~ 1, dat.sp, cutoff = plot.wid * 10, width = plot.wid)
plot(vg, plot.numbers = TRUE,
     main="mercer.wheat.uniformity - variogram")
# }