| as.data.frame {base} | R Documentation |
Functions to check if an object is a data frame, or coerce it if possible.
as.data.frame(x, row.names = NULL, optional = FALSE) is.data.frame(x)
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) is optional. |
as.data.frame is a generic function with many methods, and
users and packages can supply further methods.
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".
As from R 1.9.0 arrays can be converted. 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.
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.
In versions of R prior to 1.4.0 logical columns were converted to factors (as in S3 but not S4).
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.