R: Coerce to a Data Frame

as.data.frame {base} | R Documentation

## Coerce to a Data Frame

### Description

Functions to check if an object is a data frame, or coerce it if possible.

### Usage

    as.data.frame(x, row.names = NULL, optional = FALSE, ...)

    ## S3 method for class 'character'
    as.data.frame(x, ...,
                  stringsAsFactors = default.stringsAsFactors())

    ## S3 method for class 'list'
    as.data.frame(x, row.names = NULL, optional = FALSE, ...,
                  cut.names = FALSE, col.names = names(x), fix.empty.names = TRUE,
                  stringsAsFactors = default.stringsAsFactors())

    ## S3 method for class 'matrix'
    as.data.frame(x, row.names = NULL, optional = FALSE,
                  make.names = TRUE, ...,
                  stringsAsFactors = default.stringsAsFactors())

    is.data.frame(x)

### Arguments

`x` | any R object.
`row.names` | `NULL` or a character vector giving the row names for the data frame. Missing values are not allowed.
`optional` | logical. If `TRUE`, setting row names and converting column names (to syntactic names: see `make.names`) is optional. Note that all of R's base package `as.data.frame()` methods use `optional` only for column names treatment, basically with the meaning of `data.frame(*, check.names = !optional)`. See also the `make.names` argument of the `matrix` method.
`...` | additional arguments to be passed to or from methods.
`stringsAsFactors` | logical: should the character vector be converted to a factor?

`cut.names` | logical or integer; indicating if column names with more than 256 (or `cut.names` if that is numeric) characters should be shortened (and the last 6 characters replaced by `" ..."`).
`col.names` | (optional) character vector of column names.
`fix.empty.names` | logical indicating if empty column names, i.e., `""` should be fixed up (in `data.frame`) or not.

`make.names` | a `logical`, i.e., one of `FALSE, NA, TRUE`, indicating what should happen if the row names (of the matrix `x`) are invalid. If they are invalid, the default, `TRUE`, calls `make.names(*, unique=TRUE)`; `make.names=NA` will use “automatic” row names and a `FALSE` value will signal an error for invalid row names.

### Details

`as.data.frame` is a generic function with many methods, and users and packages can supply further methods. For classes that act as vectors, often a copy of `as.data.frame.vector` will work as the method.

If a list is supplied, each element is converted to a column in the data frame. Similarly, each column of a matrix is converted separately. This can be overridden if the object has a class which has a method for `as.data.frame`: two examples are matrices of class `"model.matrix"` (which are included as a single column) and list objects of class `"POSIXlt"` which are coerced to class `"POSIXct"`.

Arrays can be converted to data frames. One-dimensional arrays are treated like vectors and two-dimensional arrays like matrices. Arrays with more than two dimensions are converted to matrices by ‘flattening’ all dimensions after the first and creating suitable column labels.

Character variables are converted to factor columns unless protected by `I`.

If a data frame is supplied, all classes preceding `"data.frame"` are stripped, and the row names are changed if that argument is supplied.

If `row.names = NULL`, row names are constructed from the names or dimnames of `x`, otherwise are the integer sequence starting at one. Few of the methods check for duplicated row names. Names are removed from vector columns unless `I`.

### Value

`as.data.frame` returns a data frame, normally with all row names `""` if `optional = TRUE`.

`is.data.frame` returns `TRUE` if its argument is a data frame (that is, has `"data.frame"` amongst its classes) and `FALSE` otherwise.

### References

Chambers, J. M. (1992) Data for models. Chapter 3 of Statistical Models in S eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole.

### See Also

`data.frame`, `as.data.frame.table` for the `table` method (which has additional arguments if called directly).

[Package base version 4.0.5 Index]