Description Format Details Source References Examples

Uniformity trial of wheat at Aberdeen, Idaho, 1927.

A data frame with 1500 observations on the following 3 variables.

`row`

row

`col`

column (series)

`yield`

yield in grams per plot

Yield trial conducted in 1927 near Aberdeen, Idaho. The crop was Federation wheat (C.I. no 4734). Plots were seeded on April 18 with a drill that sowed eight rows at a time. Individual rows were harvested in August and threshed with a small nursery thresher. Some authors recommend analyzing the square root of the yields.

Rows were 15 feet long, 1 foot apart.

Field width: 12 cols * 15 feet = 180 feet wide.

Field length: 125 rows * 12 in = 125 feet

Wiebe, G.A. 1935. Variation and Correlation in Grain Yield among 1,500 Wheat
Nursery Plots, *Journal of Agricultural Research*, 50, 331-357.
http://naldc.nal.usda.gov/download/IND43968632/PDF

D.A. Preece, 1981,
Distributions of final digits in data,
*The Statistician*, 30, 31–60.
http://doi.org/10.2307/2987702

Wilkinson et al. (1983).
Nearest Neighbour (NN) Analysis of Field Experiments.
*J. R. Statist. Soc. B*, 45, 151-211.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 | ```
data(wiebe.wheat.uniformity)
dat <- wiebe.wheat.uniformity
if(require(desplot)){
desplot(yield~col+row, dat,
aspect=125/180, flip=TRUE, # true aspect
main="wiebe.wheat.uniformity: yield") # row 1 is at south
}
# Preece (1981) found the last digits have an interesting distribution
# with 0 and 5 much more common than other digits.
dig <- substring(dat$yield, nchar(dat$yield))
dig <- as.numeric(dig)
hist(dig, breaks=0:10-.5, xlab="Last digit",
main="wiebe.wheat.uniformity - histogram of last digit")
table(dat$col, dig) # Table 3 of Preece
# Loess
# m3 <- loess(yield~row+col, dat)
# plot(dat$row, resid(m3), ylim=c(-300,300),
# main="wiebe.wheat.uniformity")
# Wilkinson (1983, p. 152) noted that an 8-row planter was used which
# produced a recurring pattern of row effects on yield. This can be seen
# in the high autocorrelations of row means at lag 8 and lag 16
rowm <- tapply(dat$yield, dat$row, mean)
acf(rowm, main="wiebe.wheat.uniformity row means")
# Plot the row mean against the planter row unit 1-8
require("lattice")
xyplot(rowm~rep(1:8, length=125),
main="wiebe.wheat.uniformity",
xlab="Planter row unit", ylab="Row mean yield")
``` |

agridat documentation built on May 2, 2019, 4:01 p.m.

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