base (version 3.6.2) Coerce to a Data Frame


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

Usage, row.names = NULL, optional = FALSE, …)

# S3 method for character, …, stringsAsFactors = default.stringsAsFactors())

# S3 method for list, row.names = NULL, optional = FALSE, …, cut.names = FALSE, col.names = names(x), fix.empty.names = TRUE, stringsAsFactors = default.stringsAsFactors())

# S3 method for matrix, row.names = NULL, optional = FALSE, make.names = TRUE, …, stringsAsFactors = default.stringsAsFactors())



any R object.


NULL or a character vector giving the row names for the data frame. Missing values are not allowed.


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 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.


logical: should the character vector be converted to a factor?


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 " ...").


(optional) character vector of column names.


logical indicating if empty column names, i.e., "" should be fixed up (in data.frame) or not.


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.

Value returns a data frame, normally with all row names "" if optional = TRUE. returns TRUE if its argument is a data frame (that is, has "data.frame" amongst its classes) and FALSE otherwise.

Details 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 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 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.


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, for the table method (which has additional arguments if called directly).