get_prep_info_class_gmmT_get_prep_info_class_gmmGetPrepInfoClassGmmGetPrepInfoClassGmm (Operator)

Name

get_prep_info_class_gmmT_get_prep_info_class_gmmGetPrepInfoClassGmmGetPrepInfoClassGmm — Compute the information content of the preprocessed feature vectors of a GMM.

Signature

get_prep_info_class_gmm( : : GMMHandle, Preprocessing : InformationCont, CumInformationCont)

Herror T_get_prep_info_class_gmm(const Htuple GMMHandle, const Htuple Preprocessing, Htuple* InformationCont, Htuple* CumInformationCont)

void GetPrepInfoClassGmm(const HTuple& GMMHandle, const HTuple& Preprocessing, HTuple* InformationCont, HTuple* CumInformationCont)

HTuple HClassGmm::GetPrepInfoClassGmm(const HString& Preprocessing, HTuple* CumInformationCont) const

HTuple HClassGmm::GetPrepInfoClassGmm(const char* Preprocessing, HTuple* CumInformationCont) const

HTuple HClassGmm::GetPrepInfoClassGmm(const wchar_t* Preprocessing, HTuple* CumInformationCont) const   (Windows only)

static void HOperatorSet.GetPrepInfoClassGmm(HTuple GMMHandle, HTuple preprocessing, out HTuple informationCont, out HTuple cumInformationCont)

HTuple HClassGmm.GetPrepInfoClassGmm(string preprocessing, out HTuple cumInformationCont)

Description

get_prep_info_class_gmmget_prep_info_class_gmmGetPrepInfoClassGmmGetPrepInfoClassGmmGetPrepInfoClassGmm computes the information content of the training vectors that have been transformed with the preprocessing given by PreprocessingPreprocessingPreprocessingPreprocessingpreprocessing. PreprocessingPreprocessingPreprocessingPreprocessingpreprocessing can be set to 'principal_components'"principal_components""principal_components""principal_components""principal_components" or 'canonical_variates'"canonical_variates""canonical_variates""canonical_variates""canonical_variates". The preprocessing methods are described with create_class_mlpcreate_class_mlpCreateClassMlpCreateClassMlpCreateClassMlp. The information content is derived from the variations of the transformed components of the feature vector, i.e., it is computed solely based on the training data, independent of any error rate on the training data. The information content is computed for all relevant components of the transformed feature vectors (NumComponentsNumComponentsNumComponentsNumComponentsnumComponents for 'principal_components'"principal_components""principal_components""principal_components""principal_components" and 'canonical_variates'"canonical_variates""canonical_variates""canonical_variates""canonical_variates", see create_class_gmmcreate_class_gmmCreateClassGmmCreateClassGmmCreateClassGmm), and is returned in InformationContInformationContInformationContInformationContinformationCont as a number between 0 and 1. To convert the information content into a percentage, it simply needs to be multiplied by 100. The cumulative information content of the first n components is returned in the n-th component of CumInformationContCumInformationContCumInformationContCumInformationContcumInformationCont, i.e., CumInformationContCumInformationContCumInformationContCumInformationContcumInformationCont contains the sums of the first n elements of InformationContInformationContInformationContInformationContinformationCont. To use get_prep_info_class_gmmget_prep_info_class_gmmGetPrepInfoClassGmmGetPrepInfoClassGmmGetPrepInfoClassGmm, a sufficient number of samples must be added to the GMM given by GMMHandleGMMHandleGMMHandleGMMHandleGMMHandle by using add_sample_class_gmmadd_sample_class_gmmAddSampleClassGmmAddSampleClassGmmAddSampleClassGmm or read_samples_class_gmmread_samples_class_gmmReadSamplesClassGmmReadSamplesClassGmmReadSamplesClassGmm.

InformationContInformationContInformationContInformationContinformationCont and CumInformationContCumInformationContCumInformationContCumInformationContcumInformationCont can be used to decide how many components of the transformed feature vectors contain relevant information. An often used criterion is to require that the transformed data must represent x% (e.g., 90%) of the data. This can be decided easily from the first value of CumInformationContCumInformationContCumInformationContCumInformationContcumInformationCont that lies above x%. The number thus obtained can be used as the value for NumComponentsNumComponentsNumComponentsNumComponentsnumComponents in a new call to create_class_gmmcreate_class_gmmCreateClassGmmCreateClassGmmCreateClassGmm. The call to get_prep_info_class_gmmget_prep_info_class_gmmGetPrepInfoClassGmmGetPrepInfoClassGmmGetPrepInfoClassGmm already requires the creation of a GMM, and hence the setting of NumComponentsNumComponentsNumComponentsNumComponentsnumComponents in create_class_gmmcreate_class_gmmCreateClassGmmCreateClassGmmCreateClassGmm to an initial value. However, if get_prep_info_class_gmmget_prep_info_class_gmmGetPrepInfoClassGmmGetPrepInfoClassGmmGetPrepInfoClassGmm is called, it is typically not known how many components are relevant, and hence how to set NumComponentsNumComponentsNumComponentsNumComponentsnumComponents in this call. Therefore, the following two-step approach should typically be used to select NumComponentsNumComponentsNumComponentsNumComponentsnumComponents: In a first step, a GMM with the maximum number for NumComponentsNumComponentsNumComponentsNumComponentsnumComponents is created (NumComponentsNumComponentsNumComponentsNumComponentsnumComponents for 'principal_components'"principal_components""principal_components""principal_components""principal_components" and 'canonical_variates'"canonical_variates""canonical_variates""canonical_variates""canonical_variates"). Then, the training samples are added to the GMM and are saved in a file using write_samples_class_gmmwrite_samples_class_gmmWriteSamplesClassGmmWriteSamplesClassGmmWriteSamplesClassGmm. Subsequently, get_prep_info_class_gmmget_prep_info_class_gmmGetPrepInfoClassGmmGetPrepInfoClassGmmGetPrepInfoClassGmm is used to determine the information content of the components, and with this NumComponentsNumComponentsNumComponentsNumComponentsnumComponents. After this, a new GMM with the desired number of components is created, and the training samples are read with read_samples_class_gmmread_samples_class_gmmReadSamplesClassGmmReadSamplesClassGmmReadSamplesClassGmm. Finally, the GMM is trained with train_class_gmmtrain_class_gmmTrainClassGmmTrainClassGmmTrainClassGmm.

Execution Information

Parameters

GMMHandleGMMHandleGMMHandleGMMHandleGMMHandle (input_control)  class_gmm HClassGmm, HTupleHTupleHtuple (handle) (IntPtr) (HHandle) (handle)

GMM handle.

PreprocessingPreprocessingPreprocessingPreprocessingpreprocessing (input_control)  string HTupleHTupleHtuple (string) (string) (HString) (char*)

Type of preprocessing used to transform the feature vectors.

Default value: 'principal_components' "principal_components" "principal_components" "principal_components" "principal_components"

List of values: 'canonical_variates'"canonical_variates""canonical_variates""canonical_variates""canonical_variates", 'principal_components'"principal_components""principal_components""principal_components""principal_components"

InformationContInformationContInformationContInformationContinformationCont (output_control)  real-array HTupleHTupleHtuple (real) (double) (double) (double)

Relative information content of the transformed feature vectors.

CumInformationContCumInformationContCumInformationContCumInformationContcumInformationCont (output_control)  real-array HTupleHTupleHtuple (real) (double) (double) (double)

Cumulative information content of the transformed feature vectors.

Example (HDevelop)

* Create the initial GMM
create_class_gmm (NumDim, NumClasses, NumCenters, 'full',\
                  'principal_components', NumComponents, 42, GMMHandle)
* Generate and add the training data
for J := 0 to NumData-1 by 1
    * Generate training features and classes
    * Data = [...]
    * ClassID = [...]
    add_sample_class_gmm (GMMHandle, Data, ClassID, Randomize)
endfor
write_samples_class_gmm (GMMHandle, 'samples.gtf')
* Compute the information content of the transformed features
get_prep_info_class_gmm (GMMHandle, 'principal_components',\
                         InformationCont, CumInformationCont)
* Determine Comp by inspecting InformationCont and CumInformationCont
* NumComponents = [...]
* Create the actual GMM
create_class_gmm (NumDim, NumClasses, NumCenters, 'full',\
                  'principal_components', NumComponents, 42, GMMHandle)
* Train the GMM
read_samples_class_gmm (GMMHandle, 'samples.gtf')
train_class_gmm (GMMHandle, 200, 0.0001, 0.0001, Regularize, Centers, Iter)
write_class_gmm (GMMHandle, 'classifier.gmm')

Result

If the parameters are valid, the operator get_prep_info_class_gmmget_prep_info_class_gmmGetPrepInfoClassGmmGetPrepInfoClassGmmGetPrepInfoClassGmm returns the value 2 (H_MSG_TRUE). If necessary an exception is raised.

get_prep_info_class_gmmget_prep_info_class_gmmGetPrepInfoClassGmmGetPrepInfoClassGmmGetPrepInfoClassGmm may return the error 9211 (Matrix is not positive definite) if PreprocessingPreprocessingPreprocessingPreprocessingpreprocessing = 'canonical_variates'"canonical_variates""canonical_variates""canonical_variates""canonical_variates" is used. This typically indicates that not enough training samples have been stored for each class.

Possible Predecessors

add_sample_class_gmmadd_sample_class_gmmAddSampleClassGmmAddSampleClassGmmAddSampleClassGmm, read_samples_class_gmmread_samples_class_gmmReadSamplesClassGmmReadSamplesClassGmmReadSamplesClassGmm

Possible Successors

clear_class_gmmclear_class_gmmClearClassGmmClearClassGmmClearClassGmm, create_class_gmmcreate_class_gmmCreateClassGmmCreateClassGmmCreateClassGmm

References

Christopher M. Bishop: “Neural Networks for Pattern Recognition”; Oxford University Press, Oxford; 1995.
Andrew Webb: “Statistical Pattern Recognition”; Arnold, London; 1999.

Module

Foundation