qqnorm.lme {nlme}  R Documentation 
Diagnostic plots for assessing the normality of residuals and random
effects in the linear mixedeffects fit are obtained. The
form
argument gives considerable flexibility in the type of
plot specification. A conditioning expression (on the right side of a

operator) always implies that different panels are used for
each level of the conditioning factor, according to a Trellis
display.
## S3 method for class 'lme' qqnorm(y, form, abline, id, idLabels, grid, ...)
y 
an object inheriting from class 
form 
an optional onesided formula specifying the desired type of
plot. Any variable present in the original data frame used to obtain

abline 
an optional numeric value, or numeric vector of length two. If given as a single value, a horizontal line will be added to the plot at that coordinate; else, if given as a vector, its values are used as the intercept and slope for a line added to the plot. If missing, no lines are added to the plot. 
id 
an optional numeric value, or onesided formula. If given as
a value, it is used as a significance level for a twosided outlier
test for the standardized residuals (random effects). Observations with
absolute standardized residuals (random effects) greater than the
1  value/2 quantile of the standard normal distribution are
identified in the plot using 
idLabels 
an optional vector, or onesided formula. If given as a
vector, it is converted to character and used to label the
observations identified according to 
grid 
an optional logical value indicating whether a grid should
be added to plot. Default is 
... 
optional arguments passed to the Trellis plot function. 
a diagnostic Trellis plot for assessing normality of residuals or random effects.
JosÃ© Pinheiro and Douglas Bates bates@stat.wisc.edu
fm1 < lme(distance ~ age, Orthodont, random = ~ age  Subject) ## normal plot of standardized residuals by gender qqnorm(fm1, ~ resid(., type = "p")  Sex, abline = c(0, 1)) ## normal plots of random effects qqnorm(fm1, ~ranef(.))