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data.matrix {base}

Convert a Data Frame to a Numeric Matrix
Package: 
base
Version: 
R 3.0.2

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 NULL) rownames. The default, NA, uses NULL rownames 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.

Values

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.

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.

Note

The default behaviour for data frames differs from R < 2.5.0 which always gave the result character rownames.

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)

Documentation reproduced from R 3.0.2. License: GPL-2.