| data.matrix {base} | R Documentation |
Convert a Data Frame to a Numeric Matrix
Description
Return the matrix obtained by converting all the variables in a data frame to numeric mode and then binding them together as the columns of a matrix. Factors and ordered factors are replaced by their internal codes.
Usage
data.matrix(frame, rownames.force = NA)
Arguments
frame |
a data frame whose components are logical vectors, factors or numeric vectors. |
rownames.force |
logical indicating if the resulting matrix
should have character (rather than |
Details
Supplying a data frame with columns which are not numeric, factor or logical is an error. A warning is given if any non-factor column has a class, as then information can be lost.
Value
If frame inherits from class "data.frame", an integer or
numeric matrix of the same dimensions as frame, with dimnames
taken from the row.names (or NULL, depending on
rownames.force) and names.
Otherwise, the result of as.matrix.
Note
The default behaviour for data frames differs from R < 2.5.0 which always gave the result character rownames.
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
as.matrix,
data.frame,
matrix.
Examples
DF <- data.frame(a=1:3, b=letters[10:12],
c=seq(as.Date("2004-01-01"), by = "week", len = 3),
stringsAsFactors = TRUE)
data.matrix(DF[1:2])
data.matrix(DF) # gives a warning and quotes dates as #days since 1970.