byers.apple: Diameters of apples
In agridat: Agricultural Datasets

byers.apple

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

## Not run: 
  
  library(agridat)
  data(byers.apple)
  dat <- byers.apple

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

  # Overall fixed linear trend, plus random intercept/slope deviations
  # for each apple.  Observations within each apple are correlated.
  libs(nlme)
  libs(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)

agridat documentation built on Oct. 27, 2024, 5:07 p.m.