cox.stripsplit {agridat} | R Documentation

## Strip-split plot of barley with fertilizer, calcium, and soil factors.

### Description

Strip-split plot of barley with fertilizer, calcium, and soil factors.

### Format

A data frame with 96 observations on the following 5 variables.

`rep`

  replicate, 4 levels

`soil`

  soil, 3 levels

`fert`

  fertilizer, 4 levels

`calcium`

  calcium, 2 levels

`yield`

  yield of winter barley

### Details

Four different fertilizer treatments are laid out in vertical strips, which are then split into subplots with different levels of calcium. Soil type is stripped across the split-plot experiment, and the entire experiment is then replicated three times.

Sometimes called a split-block design.

### Source

Comes from the notes of Gertrude Cox and A. Rotti.

### References

SAS/STAT(R) 9.2 User's Guide, Second Edition. Example 23.5 Strip-Split Plot. http://support.sas.com/documentation/cdl/en/statug/63033/HTML/default/viewer.htm#statug_anova_sect030.htm

### Examples

    data(cox.stripsplit)
    dat <- cox.stripsplit

    # Raw means
    aggregate(yield ~ calcium, data=dat, mean)
    aggregate(yield ~ soil, data=dat, mean)
    aggregate(yield ~ calcium, data=dat, mean)

    if(require(HH)) {
      interaction2wt(yield ~ rep + soil + fert + calcium, dat,
                     x.between=0, y.between=0,
                     main="cox.stripsplit")
    }

    # Traditional AOV
    m1 <- aov(yield~ fert*calcium*soil +
              Error(rep/(fert+soil+calcium:fert+soil:fert)),
              data=dat)
    summary(m1)

    # With balanced data, the following are all basically identical

    if(require(lme4)){
      # The 'rep:soil:fert' term causes problems...so we drop it.
      m2 <- lmer(yield ~ fert*soil*calcium + (1|rep) + (1|rep:fert) +
                   (1|rep:soil) + (1|rep:fert:calcium), data=dat)
    }

    # ----------------------------------------------------------------------------

    ## Not run:

      # afex uses Kenword-Rogers approach for denominator d.f.
      if(require(afex)){
        mixed(yield ~ fert*soil*calcium + (1|rep) + (1|rep:fert) +
                (1|rep:soil) + (1|rep:fert:calcium) + (1|rep:soil:fert), data=dat,
              control=lmerControl(check.nobs.vs.rankZ="ignore"))
        ##              Effect      stat ndf     ddf F.scaling p.value
        ## 1       (Intercept) 1350.8113   1  3.0009         1  0.0000
        ## 2              fert    3.5619   3  9.0000         1  0.0604
        ## 3              soil    3.4659   2  6.0000         1  0.0999
        ## 4           calcium    1.8835   1 12.0000         1  0.1950
        ## 5         fert:soil    1.2735   6 18.0000         1  0.3179
        ## 6      fert:calcium    4.4457   3 12.0000         1  0.0255
        ## 7      soil:calcium    0.2494   2 24.0000         1  0.7813
        ## 8 fert:soil:calcium    0.3504   6 24.0000         1  0.9027
      }

    ## End(Not run)

[Package agridat version 1.16 Index]