HR {SASmixed} | R Documentation |
The HR
data frame has 120 rows and 5 columns of the heart
rates of patients under one of three possible drug treatments.
This data frame contains the following columns:
a
,
b
and p
where p
represents the placebo.
Littel, R. C., Milliken, G. A., Stroup, W. W., and Wolfinger, R. D. (1996), SAS System for Mixed Models, SAS Institute (Data Set 3.5).
str(HR) if (require("lattice", quietly = TRUE, character = TRUE)) { xyplot(HR ~ Time | Patient, HR, type = c("g", "p", "r"), aspect = "xy", index.cond = function(x, y) coef(lm(y ~ x))[1], ylab = "Heart rate (beats/min)") } if (require("lme4", quietly = TRUE, character = TRUE)) { options(contrasts = c(unordered = "contr.SAS", ordered = "contr.poly")) ## linear trend in time print(fm1HR <- lmer(HR ~ Time * Drug + baseHR + (Time|Patient), HR)) print(anova(fm1HR)) ## Not run: fm2HR <- update(fm1HR, weights = varPower(0.5)) # use power-of-mean variance summary(fm2HR) intervals(fm2HR) # variance function does not seem significant anova(fm1HR, fm2HR) # confirm with likelihood ratio ## End(Not run) print(fm3HR <- lmer(HR ~ Time + Drug + baseHR + (Time|Patient), HR)) print(anova(fm3HR)) ## remove Drug term print(fm4HR <- lmer(HR ~ Time + baseHR + (Time|Patient), HR)) print(anova(fm4HR)) }