multiply {colorSpec}

multiply a colorSpec object by scalar, vector, or matrix

Description

multiply spectra by coefficients and return modified object

Usage

## S3 method for class 'colorSpec'
multiply( x, s )

## S3 method for class 'colorSpec'
normalize( x, norm='L1' )

Arguments

x

a colorSpec object with M spectra

s

a scalar, an M-vector, or an MxP matrix. In the case of a matrix, assigning colnames(s) is recommended; see Details.

norm

one of 'L1', 'L2', or 'Linf', specifying one of the standard vector norms L^1, L^2, or L^{inf}.
norm can also be a numeric wavelength (e.g. 560 nm), and then the spectrum is scaled to have value 1 at this wavelength. Of course, this is not a true vector norm.

Details

For multiply():
If s is an MxP matrix, say S, and one thinks of the spectra as organized in an NxM matrix X, then the new spectra are defined by the matrix XS, which is NxP. If the P column names of s are set, then they are copied to the specnames of the output. Otherwise, default spectrum names are assigned as in colorSpec(), with a warning.
If s is an M-vector, then S=diag(s) is computed and used in the previous sentence. This has the effect of multiplying spectrum i by s[i].
If s is a scalar then every spectrum is multiplied by s.
The multiplication may produce negative entries, but no check is made for this.
WARNING: An M-vector and an Mx1 matrix may yield quite different results.

For normalize():
normalize() calls multiply() with s = an M-vector. If the norm of a spectrum is 0, then it is left unchanged.

Value

multiply returns a colorSpec object with the matrix of spectra of x multiplied by s.

normalize returns a colorSpec object with each spectrum of x scaled to have given norm equal to 1.

In both functions, the quantity and wavelength are preserved.

Note

If x is organized as a matrix, and s is a scalar, the one can use the simpler and equivalent s*x.

See Also

product(), quantity(), wavelength(), specnames(), colorSpec()