data.matrix {base} | R Documentation |
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.
data.matrix(frame, rownames.force = NA)
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 , uses NULL
rownames if the data frame has ‘automatic’ row.names or for a
zero-row data frame. |
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.
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
.
The default behaviour for data frames differs from R < 2.5.0 which always gave the result character rownames.
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.
as.matrix
,
data.frame
,
matrix
.
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.