R: Scaling and Centering of Matrix-like Objects

scale {base} | R Documentation

## Scaling and Centering of Matrix-like Objects

### Description

`scale` is generic function whose default method centers and/or scales the columns of a numeric matrix.

### Usage

    scale(x, center = TRUE, scale = TRUE)

### Arguments

`x` | a numeric matrix(like object).
`center` | either a logical value or numeric-alike vector of length equal to the number of columns of `x`, where ‘numeric-alike’ means that `as.numeric(.)` will be applied successfully if `is.numeric(.)` is not true.
`scale` | either a logical value or a numeric-alike vector of length equal to the number of columns of `x`.

### Details

The value of `center` determines how column centering is performed. If `center` is a numeric-alike vector with length equal to the number of columns of `x`, then each column of `x` has the corresponding value from `center` subtracted from it. If `center` is `TRUE` then centering is done by subtracting the column means (omitting `NA`s) of `x` from their corresponding columns, and if `center` is `FALSE`, no centering is done.

The value of `scale` determines how column scaling is performed (after centering). If `scale` is a numeric-alike vector with length equal to the number of columns of `x`, then each column of `x` is divided by the corresponding value from `scale`. If `scale` is `TRUE` then scaling is done by dividing the (centered) columns of `x` by their standard deviations if `center` is `TRUE`, and the root mean square otherwise. If `scale` is `FALSE`, no scaling is done.

The root-mean-square for a (possibly centered) column is defined as sqrt(sum(x^2)/(n-1)), where x is a vector of the non-missing values and n is the number of non-missing values. In the case `center = TRUE`, this is the same as the standard deviation, but in general it is not. (To scale by the standard deviations without centering, use `scale(x, center = FALSE, scale = apply(x, 2, sd, na.rm = TRUE))`.)

### Value

For `scale.default`, the centered, scaled matrix. The numeric centering and scalings used (if any) are returned as attributes `"scaled:center"` and `"scaled:scale"`

### References

Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.

### See Also

`sweep` which allows centering (and scaling) with arbitrary statistics.

For working with the scale of a plot, see `par`.

### Examples

    require(stats)
    x <- matrix(1:10, ncol = 2)
    (centered.x <- scale(x, scale = FALSE))
    cov(centered.scaled.x <- scale(x)) # all 1

[Package base version 3.5.1 Index]