piepho.cocksfoot {agridat} | R Documentation

## Heading dates for cock's foot on 25 varieties in 7 years

### Description

Heading dates for cock's foot on 25 varieties in 7 years

### Usage

    data("piepho.cocksfoot")

### Format

A data frame with 111 observations on the following 3 variables.

`gen`

  genotype factor, 25 levels

`year`

  year, numeric

`date`

  heading date (days from April 1)

### Details

These data are heading dates (days from April 1 to heading) of 25 cock's foot Dactylis glomerata varieties in trials at Hannover, Germany, repeated over seven years. Values are means over replications.

### Source

Hans-Pieter Piepho. (1999). Fitting a Regression Model for Genotype-by-Environment Data on Heading Dates in Grasses by Methods for Nonlinear Mixed Models. Biometrics, 55, 1120-1128. http://doi.org/10.1111/j.0006-341X.1999.01120.x

### Examples

    data(piepho.cocksfoot)
    dat <- piepho.cocksfoot
    dat$env <- factor(dat$year)

    require(lattice)
    densityplot(~date|env, data=dat, main="piepho.cocksfoot - heading date") # Gaussian, not gamma distn

    ## Not run:
      require(lme4)
      # A simple mixed model gives results similar to Piepho, Table 2.
      m1 <- lmer(date ~ -1 + gen + (1|env), data=dat)
      summary(m1)
      ## Fixed effects:
      ##        Estimate Std. Error t value
      ## genG01   48.951      1.744   28.07
      ## genG02   42.270      1.755   24.09
      ## genG03   45.293      1.744   25.98
      ## genG04   45.467      1.744   26.08
      ## genG05   44.215      1.755   25.20

    ## End(Not run)

[Package agridat version 1.16 Index]