R: Normalize Rows or Columns of Matrix to Unit Length...

normalize.rows {wordspace} | R Documentation

## Normalize Rows or Columns of Matrix to Unit Length (wordspace)

### Description

Efficiently normalize the row or column vectors of a dense or sparse matrix to unit length.

### Usage

    normalize.rows(M, method = "euclidean", p = 2, ...,
                   tol = 1e-6, inplace = FALSE)

    normalize.cols(M, method = "euclidean", p = 2, ...,
                   tol = 1e-6, inplace = FALSE)

### Arguments

`M` | a dense or sparse numeric matrix
`method` | norm to be computed, see `rowNorms`
`p` | exponent of Minkowski p-norm in the range 0 < p ≤ ∞. Note that normalization is not possible for very small values of p.
`...` | any further arguments are passed to `rowNorms` (or `colNorms`)
`tol` | row/column vectors with norm below `tol` are assumed to be all zeroes and cannot be normalized (see “Details” below)
`inplace` | if `TRUE`, modify the matrix `M` in place. Don't ever set this argument to `TRUE`.

### Details

These functions return a matrix with row (or column) vectors rescaled to a length of 1 according to the selected norm.

All-zero vectors (with |0| = 0) cannot be normalized. In order to avoid scaling up rounding errors, rows (or columns) with |x| < tol are explicitly set to 0 (and thus not normalized). Since a suitable threshold for rounding errors depends on the scaling behaviour of the selected norm and the provenance of M, it is advisable to set `tol` explicitly to an appropriate value. Pass `tol = 0` to normalize all nonzero vectors.

The generalized Minkowski norm with p < 1 is not homogeneous but can still be normalized. This is numerically unstable for very small values of p, which will be rejected with an error message. The Hamming length (p = 0) cannot be normalized at all. See `rowNorms` for more information.

### Value

A row-normalized (or column-normalized) matrix with the same dimensions as M.

### Author(s)

Stefan Evert (http://purl.org/stefan.evert)

### See Also

See `rowNorms` for details on available norms and their parameters.

[Package wordspace version 0.2-6 Index]