data.matrix
Convert a Data Frame to a Numeric Matrix
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.
 Keywords
 array
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
NULL
)rownames
. The default,NA
, usesNULL
rownames if the data frame has ‘automatic’ row.names or for a zerorow data frame.
Details
Logical and factor columns are converted to integers. Any other
column which is not numeric (according to is.numeric
) is
converted by as.numeric
or, for S4 objects,
as(, "numeric")
. If all columns are integer (after
conversion) the result is an integer matrix, otherwise a numeric
(double) matrix.
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
Examples
library(base)
DF < data.frame(a = 1:3, b = letters[10:12],
c = seq(as.Date("20040101"), by = "week", len = 3),
stringsAsFactors = TRUE)
data.matrix(DF[1:2])
data.matrix(DF)