baseball {BradleyTerry2} | R Documentation |
Baseball results for games in the 1987 season between 7 teams in the Eastern Division of the American League.
baseball
A data frame with 42 observations on the following 4 variables.
home.team
a factor with levels Baltimore
,
Boston
, Cleveland
, Detroit
,
Milwaukee
, New York
, Toronto
.
away.team
a factor with levels Baltimore
,
Boston
, Cleveland
, Detroit
,
Milwaukee
, New York
, Toronto
.
home.wins
a numeric vector.
away.wins
a numeric vector.
This dataset is in a simpler format than the one described in Firth (2005).
Page 438 of Agresti, A. (2002) Categorical Data Analysis (2nd Edn.). New York: Wiley.
Firth, D. (2005) Bradley-Terry models in R. Journal of Statistical Software, 12(1), 1–12.
Turner, H. and Firth, D. (2012) Bradley-Terry models in R: The BradleyTerry2 package. Journal of Statistical Software, 48(9), 1–21.
## This reproduces the analysis in Sec 10.6 of Agresti (2002). ## Simple Bradley-Terry model, ignoring home advantage: baseballModel1 <- BTm(cbind(home.wins, away.wins), home.team, away.team, data = baseball, id = "team") ## Now incorporate the "home advantage" effect baseball$home.team <- data.frame(team = baseball$home.team, at.home = 1) baseball$away.team <- data.frame(team = baseball$away.team, at.home = 0) baseballModel2 <- update(baseballModel1, formula = ~ team + at.home) ## Compare the fit of these two models: anova(baseballModel1, baseballModel2)