R: Summarize by Groups

gsummary {nlme} | R Documentation

## Summarize by Groups

### Description

Provide a summary of the variables in a data frame by groups of rows. This is most useful with a `groupedData` object to examine the variables by group.

### Usage

    gsummary(object, FUN, omitGroupingFactor, form, level,
       groups, invariantsOnly, ...)

### Arguments

`object` | an object to be summarized - usually a `groupedData` object or a `data.frame`.
`FUN` | an optional summary function or a list of summary functions to be applied to each variable in the frame. The function or functions are applied only to variables in `object` that vary within the groups defined by `groups`. 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 non-invariant 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 frame such as `ordered`, `factor`, or `numeric`. The indicated function will be applied to any non-invariant 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 S-language mode of the variable.
`omitGroupingFactor` | an optional logical value. When `TRUE` the grouping factor itself will be omitted from the group-wise summary but the levels of the grouping factor will continue to be used as the row names for the data frame that is produced by the summary. Defaults to `FALSE`.
`form` | an optional one-sided formula that defines the groups. When this formula is given, the right-hand side is evaluated in `object`, converted to a factor if necessary, and the unique levels are used to define the groups. Defaults to `formula(object)`.
`level` | an optional positive integer giving the level of grouping to be used in an object with multiple nested grouping levels. Defaults to the highest or innermost level of grouping.
`groups` | an optional factor that will be used to split the rows into groups. Defaults to `getGroups(object, form, level)`.
`invariantsOnly` | an optional logical value. When `TRUE` only those covariates that are invariant within each group will be summarized. The summary value for the group is always the unique value taken on by that covariate within the group. The columns in the summary are of the same class as the corresponding columns in `object`. By definition, the grouping factor itself must be an invariant. When combined with `omitGroupingFactor = TRUE`, this option can be used to discover is there are invariant covariates in the data frame. Defaults to `FALSE`.
`...` | optional additional arguments to the summary functions that are invoked on the variables by group. Often it is helpful to specify `na.rm = TRUE`.

### Value

A `data.frame` with one row for each level of the grouping factor. The number of columns is at most the number of columns in `object`.

### Author(s)

Jose Pinheiro and Douglas Bates bates@stat.wisc.edu

### References

Pinheiro, J.C., and Bates, D.M. (2000) "Mixed-Effects Models in S and S-PLUS", Springer.

### See Also

`summary`, `groupedData`, `getGroups`

### Examples

    gsummary(Orthodont)  # default summary by Subject
    ## gsummary with invariantsOnly = TRUE and omitGroupingFactor = TRUE
    ## determines whether there are covariates like Sex that are invariant
    ## within the repeated observations on the same Subject.
    gsummary(Orthodont, inv = TRUE, omit = TRUE)

[Package nlme version 3.1-104 Index]