datafiles.m

这是模式识别方面的电子书籍

%DATAFILES Info on the datafile class construction for PRTools
%
% This is not a command, just an information file.
%
% Datafiles in PRTools are in the MATLAB language defined as objects of the
% class DATAFILE. They inherit most of their properties of the class DATASET.
% They are a generalisation of this class allowing for large datasets 
% distributed over a set of files. Before conversion to a dataset 
% preprocessing can be defined. There are four types of datafiles:
% raw : Every file is interpreted as a single object in the dataset. These
%       files may, for instance, be images of different size.
% cell: All files should be mat-files containing just a single variable being
%       a cell array. Its elements are interpreted as objects. The file names 
%       will be used as labels during construction. This may be changed by the
%       user afterwards.
% pre-cooked : In this case the user should supply a command that reads a
%       file and converts it to a dataset.
% half-baked : All files should be mat-files, containing a single dataset. 
% mature : This is a datafile by PRTools, using the SAVEDATAFILE command after
%       execution of all preprocessing defined for the datafile. 
%
% A datafile is, like a dataset, a set consisting of M objects, each described
% by K features. K might be unknown, in which case it is set to zero, K=0.
% Datafiles store an administration about the files or directories in which
% the objects are stored. In addition they can store commands to preprocess
% the files before they are converted to a dataset and postprocessing
% commands, to be executed after conversion to a dataset.
%
% Datafiles are mainly an administration. Operations on datafiles are
% possible as long as they can be stored (e.g. filtering of images for raw
% datafiles, or object selection by GENDAT). Commands that are able to
% process objects sequentially, like NMC and TESTC can be executed on
% datafiles.
%
% Whenever a raw datafile is sufficiently defined by pre- and postprocessing
% it can be converted into a dataset. If this is still a large dataset, not
% suitable for the available memory, it should be stored by the
% SAVEDATAFILE command and is ready for later use. If the dataset is
% sufficiently small it can be directly converted into a dataset by
% DATASET.
%
% Intermediate results of datafiles that by the defined preprocessing
% cannot yet be converted into a dataset, can be stored as a new, raw
% datafile by CREATEDATAFILE.
%
% The main commands specific for datafiles are:
% DATAFILE      - constructor. It defines a datafile on a directory.
% ADDPREPROC    - adds preprocessing commands (low level command)
% ADDPOSTPROC   - adds postprocessing commands (low level command)
% FILTM         - user interface to add preprocessing to a datafile.
% CREATEDATAFILE- executes all defined preprocessing and stores the result
%                 as a new, raw datafile.
% SAVEDATAFILE  - executes all defined pre- and postprocessing and stores
%                 the result as a dataset in a set of matfiles.
% DATASET       - conversion to dataset
%
% Datafiles have the following fields, in addition to all dataset fields.
% ROOTPATH      - Absolute path of the datafile
% FILES         - names of directories (for raw datafiles) or mat-files
%                 (for converted datafiles)
% TYPE          - datafile type
% PREPROC       - preprocessing commands in a struct array
% POSTPROC      - postprocessing commands as mappings
% DATASET       - stores all dataset fields. Note that the DATA field as well
%                 as the target field are empty and that the IDENT.FILE_INDEX 
%                 field is used to store for every object a pointer to a file 
%                 or directory in FILES.
%
% Almost all operations defined for datasets are also defined for
% datafiles, with a few exceptions. Also fixed and trained mappings can
% handle datafiles, as they process objects sequentially. The use of
% untrained mappings in combination with datafiles is a problem, as they
% have to be adapted to the sequential use of the objects. Mappings that
% can handle datafiles are indicated in the Contents file.
%
% The possibility to define preprocessing of objects (e.g. images) with
% different sizes makes datafiles useful for handling raw data and
% measurements of features.

% Copyright: R.P.W. Duin, [e-mail]
% Faculty EWI, Delft University of Technology
% P.O. Box 5031, 2600 GA Delft, The Netherlands