npreprocess
Purpose
Preprocessing of multi-way arrays.
Synopsis
[prex,prepar] = npreprocess(x,prepar,undo,options)
prex = npreprocess(x,setting)
prex = npreprocess(x,prepar)
prex = npreprocess(x,prepar,1)
options = npreprocess('options')
Description
NPREPROCESS is used for three different purposes:
1) for centering and scaling multi-way arrays in which case
the parameters (offsets and scales) are first calculated and then applied to
the data,
2) for preprocessing another data set according to (1), and
3) for transforming preprocessed data back (undo
preprocessing).
INPUTS:
x = data array, and
settings
= a two-row matrix (class "double") indicating which modes to
center and scale. The matrix is: settings = [cent; scal]. E.g.
settings(1,:) = [1 0 1] => center across
mode one and three, and
settings(2,:) = [1 1 0] => scale to unit
variance within mode one and two.
OPTIONAL INPUTS:
prepar = contains earlier defined mean and
scale parameters, this data is required for applying or undoing preprocessing,
undo = when set to 1 this flag tells to undo/transform
back, and
options = discussed below.
OUTPUTS:
prex = the preprocessed data, and
prepar = a structure containing the necessary parameters to
pre- and post-process other arrays.
Options
options = a structure array with the following fields:
name: 'options', identifies the structure as an options structure,
display: [
{'on'} | 'off' ], governs level of display,
iterproc: [
'on' | {'off'} ], allows iterative preprocessing which is necessary for
some combinations of centering and scaling (see User Manual),
scalefirst: [ {'on'} | 'off' ], defines that scaling is done before
centering which may have implications in complex combinations of preprocessing
(see User Manual), and
usemse: [ {'on'} | 'off' ], defines
that mean square scaling is used instead of scaling by standard deviations as
is common in two-way analysis.
Examples
To apply preprocessing with options:
[prex,prepar] = npreprocess(x,settings,[],0,options);
See Also
auto, mncn, preprocess, rescale, scale
