Split strip plot on soybeans

Description

Split strip plot on soybeans

Format

A data frame with 160 observations on the following 8 variables.

block

block factor, 4 levels

plot

plot number

cultivar

cultivar factor, 4 levels

spacing

row spacing, numeric

pop

population, numeric (thousand per acre)

yield

yield, a numeric vector

row

row number

col

column number

Details

Within each block, cultivars were whole plots. Withing whole plots, spacing was applied in strips vertically, and population was applied in strips horizontally.

Source

Schabenberger, Oliver and Francis J. Pierce. 2002. Contemporary Statistical Models for the Plant and Soil Sciences. CRC Press, Boca Raton, FL. Page 493.

Used with permission of David Holshouser at Virginia Polytechnic.

Examples

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data(holshouser.splitstrip)
dat <- holshouser.splitstrip
dat$spacing <- factor(dat$spacing)
dat$pop <- factor(dat$pop)

# Experiment layout and field trends
desplot(spacing ~ col*row, data=dat, out1=block, out2=cultivar,
        col=cultivar, text=pop, cex=.8, shorten='none', col.regions=c('wheat','white'),
        main="holshouser.splitstrip experiment design")
desplot(yield ~ col*row, data=dat, out1=block,
        main="holshouser.splitstrip")

# Overall main effects and interactions
require(HH)
interaction2wt(yield~cultivar*spacing*pop, dat,
               main="holshouser.splitstrip")

## Schabenberger's SAS model, page 497
## proc mixed data=splitstripplot;
##   class block cultivar pop spacing;
##   model yield = cultivar spacing spacing*cultivar pop pop*cultivar
##                 spacing*pop spacing*pop*cultivar / ddfm=satterth;
##   random block block*cultivar block*cultivar*spacing block*cultivar*pop;
## run;

## Now lme4. This design has five error terms--four are explicitly given.
if(require(lme4) & require(lucid)){
m1 <- lmer(yield ~ cultivar * spacing * pop +
           (1|block) + (1|block:cultivar) + (1|block:cultivar:spacing) +
           (1|block:cultivar:pop), data=dat)
vc(m1) ## Variances match Schabenberger, page 498.
##                    grp        var1 var2   vcov  sdcor
##     block:cultivar:pop (Intercept) <NA> 2.421  1.556
## block:cultivar:spacing (Intercept) <NA> 1.244  1.116
##         block:cultivar (Intercept) <NA> 0.4523 0.6725
##                  block (Intercept) <NA> 3.037  1.743
##               Residual        <NA> <NA> 3.928  1.982

}

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