Normalization Filter

Normalizes inputs spectral data.

Category	Preprocessing
Node
Parameters	Method: which extrema to find. If set to Global extrema the minimum and maximum values of the input (or fit input) will be determined. If set to Local extrema the largest local maximum and the smallest local minimum of the input (or the fit input) will be determined. NewMinimum: the target minimum value. The spectrum will be scaled and shifted so that the previous global or local minimum is mapped to this target value NewMaximum: the target maximum value. The spectrum will be scaled and shifted so that the previous global or local maximum is mapped to this target value. Delta: when searching for local extrema in the input (or the fit input) this denotes a minimum distance (in the ordinate direction) between extrema, so that a newly found extremum is considered to be more than just noise. Fit input: if off the filter has only one input that is used for both determining the extrema as well as to apply the scaling and shifting. If on the filter has two inputs: the second input will be used to determine the extrema, and the resulting shift and scaling factor will then be applied to the first input.
Inputs	Input (if the Fit input parameter is disabled): the input of the filter (both for fitting and for applying the normalization) Apply Input (if the Fit input parameter is enabled): the input to apply the shift and scaling factor to Fit Input (if the Fit input parameter is enabled): the input used to determine the extrema
Outputs	Output: the normalized data

Effect of the Filter

For each pixel the filter will calculate the global or local extrema of the spectrum. The following plot shows how local and global extrema work:

The filter will then scale and shift the spectrum according to the following formula:

$N(\lambda) = (f(\lambda) - m) / (M - m) * (K - k) + k$

where $f(\lambda)$ is the input spectrum, $m$ is the minimum that was determined for the spectrum, $M$ is the maximum that was determined for the spectrum, $K$ is the value of the NewMaximum parameter and $k$ is the value of the NewMinimum parameter.

The following plot shows the result of the normalization filter when the Method parameter is set to Global extrema:

The following plot shows the result of the normalization filter when the Method parameter is set to Local extrema:

Normalization Filter

Effect of the Filter

See also