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, usesNULLrownames if the data frame has ‘automatic’ row.names or for a zero-row 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)
# NOT RUN {
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)
# }