agridat (version 1.5)

gomez.uniformity: Rice uniformity yield test

Description

An area 20 meters by 38 meters was planted to rice variety IR8. At harvest, a 1-meter border was removed around the field and discarded. Each square meter (1 meter by 1 meter) was harvested and weighed.

Usage

data(gomez.uniformity)

source

Gomez, K.A. and Gomez, A.A.. 1984, Statistical Procedures for Agricultural Research. Wiley-Interscience. Page 481. Used with permission of Kwanchai Gomez.

Examples

dat <- gomez.uniformity

# Raw data plot
require("lattice")
desplot(yield ~ x*y, data=dat, aspect=38/20)

# 3x3 moving average.  Gomez figure 12.1
require("reshape2")
dmat <- melt(dat, id.var=c('x','y'))
dmat <- acast(dmat, y~x)
m0 <- dmat
cx <- 2:17
rx <- 2:35
dmat3 <- (m0[rx+1,cx+1]+m0[rx+1,cx]+m0[rx+1,cx-1]+
          m0[rx,cx+1]+m0[rx,cx]+m0[rx,cx-1]+
          m0[rx-1,cx+1]+m0[rx-1,cx]+m0[rx-1,cx-1])/9
dat3 <- melt(dmat3)
desplot(value~Var2*Var1, dat3, at=c(576,637,695,753,811,870,927))

require("agricolae")

# Gomez table 12.4
tab <- index.smith(dmat, col="red")$uniformity
tab <- data.frame(tab)

# Gomez figure 12.2
par(mar=c(5,4,4,4)+.1)
m1 <- nls(Vx ~ 9041/Size^b, data=tab, start=list(b=1))
plot(Vx ~ Size, tab, xlab="Plot size, m^2")
lines(fitted(m1) ~ tab$Size, col='red')
axis(4, at=tab$Vx, labels=tab$CV)
mtext("CV", 4, line=2)