Body Weights of 48 Pigs in 9 Successive Weeks

This data set appears in Table 3.1 of Diggle, Liang, and Zeger (1994).

Usage

data("Pigs", package = "cv")

Format

A data frame with 432 rows and 3 columns.

id: Pig id number, 1–48.
week: Week number, 1–9.
weight: Weight in kg.

Source

P. J. Diggle, K.-Y. Liang, and S. L. Zeger, Analysis of Longitudinal Data (Oxford, 1994).

Examples

library("lme4")
#> Loading required package: Matrix
m.p <- lmer(weight ~ week + (1 | id) + (1 | week),
            data=Pigs, REML=FALSE,
            control=lmerControl(optimizer="bobyqa"))
summary(m.p)
#> Linear mixed model fit by maximum likelihood  ['lmerMod']
#> Formula: weight ~ week + (1 | id) + (1 | week)
#>    Data: Pigs
#> Control: lmerControl(optimizer = "bobyqa")
#> 
#>      AIC      BIC   logLik deviance df.resid 
#>   2037.6   2058.0  -1013.8   2027.6      427 
#> 
#> Scaled residuals: 
#>     Min      1Q  Median      3Q     Max 
#> -3.7750 -0.5418  0.0054  0.4762  3.9816 
#> 
#> Random effects:
#>  Groups   Name        Variance Std.Dev.
#>  id       (Intercept) 14.83622 3.8518  
#>  week     (Intercept)  0.08499 0.2915  
#>  Residual              4.29733 2.0730  
#> Number of obs: 432, groups:  id, 48; week, 9
#> 
#> Fixed effects:
#>             Estimate Std. Error t value
#> (Intercept) 19.35561    0.63340   30.56
#> week         6.20990    0.05393  115.14
#> 
#> Correlation of Fixed Effects:
#>      (Intr)
#> week -0.426
cv(m.p, clusterVariables=c("id", "week"), k=10, seed=8469)
#> R RNG seed set to 8469
#> cross-validation criterion (mse) = 19.2352