# data.matrix {base}

### 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.

### See Also

### 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.