byers.apple {agridat} | R Documentation

## Diameters of apples

### Description

Measurements of the diameters of apples

### Format

A data frame with 480 observations on the following 6 variables.

`tree`

  tree, 10 levels

`apple`

  apple, 24 levels

`size`

  size of apple

`appleid`

  unique id number for each apple

`time`

  time period, 1-6 = (week/2)

`diameter`

  diameter, inches

### Details

Experiment conducted at the Winchester Agricultural Experiment Station of Virginia Polytechnic Institute and State University. Twentyfive apples were chosen from each of ten apple trees.

Of these, there were 80 apples in the largest size class, 2.75 inches in diameter or greater.

The diameters of the apples were recorded every two weeks over a 12-week period.

### Source

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

### Examples

    data(byers.apple)
    dat <- byers.apple

    require(lattice)
    xyplot(diameter ~ time | factor(appleid), data=dat, type=c('p','l'),
           strip=strip.custom(par.strip.text=list(cex=.7)),
           main="byers.apple")

    ## Not run:
      # Overall fixed linear trend, plus random intercept/slope deviations
      # for each apple.  Observations within each apple are correlated.
      require(nlme)
      require(lucid)
      m1 <- lme(diameter ~ 1 + time, data=dat,
                random = ~ time|appleid, method='ML',
                cor = corAR1(0, form=~ time|appleid),
                na.action=na.omit)
      vc(m1)
      ##       effect   variance   stddev corr
      ##  (Intercept) 0.007354   0.08575    NA
      ##         time 0.00003632 0.006027 0.83
      ##     Residual 0.0004555  0.02134    NA

    ## End(Not run)

[Package agridat version 1.16 Index]