scale                  package: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 a numeric vector of length equal to
          the number of columns of `x'.

   scale: either a logical value or a numeric 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 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 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 root-mean-square, and if `scale' is `FALSE', no
     scaling is done.

     The root-mean-square for a column is obtained by computing the
     square-root of the sum-of-squares of the non-missing values in the
     column divided by the number of non-missing values minus one.

Value:

     For `scale.default', the centered, scaled matrix.

See Also:

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

Examples:

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

