data.matrix               package:base               R Documentation

Data Frame to 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)

Arguments:

   frame: a data frame whose components are logical vectors, factors or
          numeric vectors.

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' is a data frame, a numeric matrix of the same
     dimensions as 'frame', with dimnames taken from the row.names and
     names.

     Otherwise, the result of 'as.matrix'.

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.

