collapse.groupedData {nlme}  R Documentation 
If object
has a single grouping factor, it is returned
unchanged. Else, it is summarized by the values of the
displayLevel
grouping factor (or the combination of its values
and the values of the covariate indicated in preserve
, if any is
present). The collapsed data is used to produce a new
groupedData
object, with grouping factor given by the
displayLevel
factor.
## S3 method for class 'groupedData': collapse(object, collapseLevel, displayLevel, outer, inner, preserve, FUN, subset, ...)
object 
an object inheriting from class groupedData ,
generally with multiple grouping factors.

collapseLevel 
an optional positive integer or character string indicating the grouping level to use when collapsing the data. Level values increase from outermost to innermost grouping. Default is the highest or innermost level of grouping. 
displayLevel 
an optional positive integer or character string
indicating the grouping level to use as the grouping factor for the
collapsed data. Default is collapseLevel .

outer 
an optional logical value or onesided formula,
indicating covariates that are outer to the displayLevel
grouping factor. If equal to TRUE , the displayLevel
element attr(object, "outer") is used to indicate the
outer covariates. An outer covariate is invariant within the sets
of rows defined by the grouping factor. Ordering of the groups is
done in such a way as to preserve adjacency of groups with the same
value of the outer variables. Defaults to NULL , meaning that
no outer covariates are to be used.

inner 
an optional logical value or onesided formula, indicating
a covariate that is inner to the displayLevel grouping
factor. If equal to TRUE , attr(object, "outer") is used
to indicate the inner covariate. An inner covariate can change within
the sets of rows defined by the grouping factor. Defaults to
NULL , meaning that no inner covariate is present.

preserve 
an optional onesided formula indicating a covariate
whose levels should be preserved when collapsing the data according
to the collapseLevel grouping factor. The collapsing factor is
obtained by pasting together the levels of the collapseLevel
grouping factor and the values of the covariate to be
preserved. Default is NULL , meaning that no covariates need to
be preserved.

FUN 
an optional summary function or a list of summary functions
to be used for collapsing the data. The function or functions are
applied only to variables in object that vary within the
groups defined by collapseLevel . Invariant variables are
always summarized by group using the unique value that they assume
within that group. If FUN is a single
function it will be applied to each noninvariant variable by group
to produce the summary for that variable. If FUN is a list of
functions, the names in the list should designate classes of
variables in the data such as ordered , factor , or
numeric . The indicated function will be applied to any
noninvariant variables of that class. The default functions to be
used are mean for numeric factors, and Mode for both
factor and ordered . The Mode function, defined
internally in gsummary , returns the modal or most popular
value of the variable. It is different from the mode function
that returns the Slanguage mode of the variable. 
subset 
an optional named list. Names can be either positive
integers representing grouping levels, or names of grouping
factors. Each element in the list is a vector indicating the levels
of the corresponding grouping factor to be preserved in the collapsed
data. Default is NULL , meaning that all levels are
used.

... 
some methods for this generic require additional arguments. None are used in this method. 
a groupedData
object with a single grouping factor given by the
displayLevel
grouping factor, resulting from collapsing
object
over the levels of the collapseLevel
grouping
factor.
Jose Pinheiro Jose.Pinheiro@pharma.novartis.com and Douglas Bates bates@stat.wisc.edu
Pinheiro, J.C. and Bates, D.M. (1997) "Future Directions in MixedEffects Software: Design of NLME 3.0" available at http://franz.stat.wisc.edu/pub/NLME.
groupedData
, plot.nmGroupedData
# collapsing by Dog collapse(Pixel, collapse = 1) # same as collapse(Pixel, collapse = "Dog")