piepho.cocksfoot {agridat} | R Documentation |
Heading dates for cock's foot on 25 varieties in 7 years
data("piepho.cocksfoot")
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)
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.
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
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)