timeFrequencyScalarFeatureOptions
Store information for converting time-frequency-domain feature vectors to scalar values
Since R2024a
Description
Use a timeFrequencyScalarFeatureOptions
object to store methods to convert
time-frequency-domain feature vectors to scalars. You can use the resulting
timeFrequencyScalarFeatureOptions
object to set the ScalarizationMethod
property of a signalTimeFrequencyFeatureExtractor
object.
Creation
Description
creates an object opts
= timeFrequencyScalarFeatureOptionsopts
that stores the scalarization methods with
default values (empty string arrays) for all signal features in time-frequency
domain.
specifies scalarization methods for each time-frequency domain signal feature using
name-value arguments. You can specify multiple name-value arguments. For example,
opts
= timeFrequencyScalarFeatureOptions(Name=Value
)timeFrequencyScalarFeatureOptions(SpectralCrest=["Mean"
"Energy"],TFRidges="Kurtosis")
specifies "Mean"
and
"Energy"
as scalarization methods for the spectral crest feature, and
"Kurtosis"
as the scalarization method for the time-frequency ridge
feature. For more information about scalarization methods, see Scalarization Methods for Domain-Specific Signal Features.
Properties
SpectralKurtosis
— Scalarization methods for spectral kurtosis feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the spectral kurtosis feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the spectral kurtosis feature, see spectralKurtosis
.
Example: SpectralKurtosis = ["Mean" "PeakValue"]
sets the option
to extract the mean and the peak value of the spectral kurtosis feature
vector.
Data Types: cell
| string
SpectralSkewness
— Scalarization methods for spectral skewness feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the spectral skewness feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the spectral skewness feature, see spectralSkewness
.
Example: SpectralSkewness = ["Mean" "PeakValue"]
sets the option
to extract the mean and the peak value of the spectral skewness feature
vector.
Data Types: cell
| string
SpectralCrest
— Scalarization methods for spectral crest feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the spectral crest feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the spectral crest feature, see spectralCrest
.
Example: SpectralCrest = ["Mean" "PeakValue"]
sets the option to
extract the mean and the peak value of the spectral crest feature
vector.
Data Types: cell
| string
SpectralFlatness
— Scalarization methods for spectral flatness feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the spectral flatness feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the spectral flatness feature, see spectralFlatness
.
Example: SpectralFlatness = ["Mean" "PeakValue"]
sets the option
to extract the mean and the peak value of the spectral flatness feature
vector.
Data Types: cell
| string
SpectralEntropy
— Scalarization methods for spectral entropy feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the spectral entropy feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the spectral entropy feature, see spectralEntropy
.
Example: SpectralEntropy = ["Mean" "PeakValue"]
sets the option
to extract the mean and the peak value of the spectral entropy feature
vector.
Data Types: cell
| string
TFRidges
— Scalarization methods for time-frequency ridges feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the time-frequency ridges feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the time-frequency ridge feature, see tfridge
.
Example: TFRidges = ["Mean" "PeakValue"]
sets the option to
extract the mean and the peak value of the time-frequency ridge feature
vector.
Data Types: cell
| string
InstantaneousBandwidth
— Scalarization methods for instantaneous bandwidth feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the instantaneous bandwidth feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the instantaneous bandwidth feature, see instbw
.
Example: InstantaneousBandwidth = ["Mean" "PeakValue"]
sets the
option to extract the mean and the peak value of the instantaneous bandwidth feature
vector.
Data Types: cell
| string
InstantaneousFrequency
— Scalarization methods for instantaneous frequency feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the instantaneous frequency feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the instantaneous frequency feature, see instfreq
or hht
.
Example: InstantaneousFrequency = ["Mean" "PeakValue"]
sets the
option to extract the mean and the peak value of the instantaneous frequency feature
vector.
Data Types: cell
| string
InstantaneousEnergy
— Scalarization methods for instantaneous energy feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the instantaneous energy feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the instantaneous energy feature, see hht
.
Example: InstantaneousEnergy = ["Mean" "PeakValue"]
sets the
option to extract the mean and the peak value of the instantaneous energy feature
vector.
Data Types: cell
| string
MeanEnvelopeEnergy
— Scalarization methods for mean envelope energy feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the mean envelope energy feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the mean envelope energy feature, see emd
.
Example: MeanEnvelopeEnergy = ["Mean" "PeakValue"]
sets the
option to extract the mean and the peak value of the mean envelope energy feature
vector.
Data Types: cell
| string
WaveletEntropy
— Scalarization methods for wavelet entropy feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the wavelet entropy feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the wavelet entropy feature, see wentropy
(Wavelet Toolbox).
Example: WaveletEntropy = ["Mean" "PeakValue"]
sets the option
to extract the mean and the peak value of the wavelet entropy feature
vector.
Data Types: cell
| string
TimeSpectrum
— Scalarization methods for time-averaged wavelet spectrum feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the time-averaged wavelet spectrum feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the time spectrum feature, see timeSpectrum
(Wavelet Toolbox).
Example: TimeSpectrum = ["Mean" "PeakValue"]
sets the option to
extract the mean and the peak value of the time spectrum feature
vector.
Data Types: cell
| string
ScaleSpectrum
— Scalarization methods for scale-averaged wavelet spectrum feature vector
strings(0)
(default) | string array | cell array
Scalarization methods for the scale-averaged wavelet spectrum feature, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on
the feature, if enabled. Enable signal features for extraction when creating the
signalTimeFrequencyFeatureExtractor
object.
If you specify this feature, the feature extractor object:
Associates with the feature any scalarization methods you have specified for it.
Appends any scalarization methods you have specified using the
All
name-value argument.
For more information about the scale spectrum feature, see scaleSpectrum
(Wavelet Toolbox).
Example: ScaleSpectrum = ["Mean" "PeakValue"]
sets the option to
extract the mean and the peak value of the scale spectrum feature
vector.
Data Types: cell
| string
All
— Scalarization methods for all signal features
strings(0)
(default) | string array | cell array
Scalarization methods for all the signal features, specified as a string array or as a cell array of character vectors.
Each element of the array corresponds to a scalarization method that you apply on all the enabled features. Enable signal features for extraction when creating the feature extractor object.
If you specify All
, the feature extractor object:
Associates the scalarization methods you have specified with all enabled features.
Appends them to the list of methods already specified for each particular feature.
Example: All = ["Mean" "PeakValue"]
sets the option to extract the mean and the peak value of all the feature vectors.
Data Types: cell
| string
Examples
Add Scalarization Methods for Time-Frequency Feature Extraction
Create a timeFrequencyScalarFeatureOptions
object with default values.
opts = timeFrequencyScalarFeatureOptions
opts = timeFrequencyScalarFeatureOptions with properties: SpectralKurtosis: [0x0 string] SpectralSkewness: [0x0 string] SpectralCrest: [0x0 string] SpectralFlatness: [0x0 string] SpectralEntropy: [0x0 string] TFRidges: [0x0 string] InstantaneousBandwidth: [0x0 string] InstantaneousFrequency: [0x0 string] InstantaneousEnergy: [0x0 string] MeanEnvelopeEnergy: [0x0 string] TimeSpectrum: [0x0 string] WaveletEntropy: [0x0 string] ScaleSpectrum: [0x0 string] All: [0x0 string]
Add scalarization methods for the spectral flatness and mean envelope energy time-frequency domain features:
opts.SpectralFlatness = "Energy"; opts.MeanEnvelopeEnergy = ["Kurtosis" "PeakValue"];
Display the list of scalarization methods for all the time-frequency features.
opts
opts = timeFrequencyScalarFeatureOptions with properties: SpectralKurtosis: [0x0 string] SpectralSkewness: [0x0 string] SpectralCrest: [0x0 string] SpectralFlatness: "Energy" SpectralEntropy: [0x0 string] TFRidges: [0x0 string] InstantaneousBandwidth: [0x0 string] InstantaneousFrequency: [0x0 string] InstantaneousEnergy: [0x0 string] MeanEnvelopeEnergy: ["Kurtosis" "PeakValue"] TimeSpectrum: [0x0 string] WaveletEntropy: [0x0 string] ScaleSpectrum: [0x0 string] All: [0x0 string]
Set Scalarization Method Property in Time-Frequency Feature Extractor Object
Create and use a timeFrequencyScalarFeatureOptions
object to set the ScalarizationMethod
property in a signalTimeFrequencyFeatureExtractor
object.
Specify the mean and the crest factor as scalar features for the spectral crest time-frequency feature. Store this information in a timeFrequencyScalarFeatureOptions
object.
opts = timeFrequencyScalarFeatureOptions( ... SpectralCrest=["Mean" "CrestFactor"]);
Create a signalTimeFrequencyFeatureExtractor
object to extract the spectral crest and time-frequency ridges with their corresponding scalar values. Display the ScalarizationMethod
property of the feature extractor object.
tfFE = signalTimeFrequencyFeatureExtractor( ... SpectralCrest=true,TFRidges=true, ... ScalarizationMethod=opts); disp(tfFE.ScalarizationMethod)
timeFrequencyScalarFeatureOptions with properties: SpectralKurtosis: [0x0 string] SpectralSkewness: [0x0 string] SpectralCrest: ["Mean" "CrestFactor"] SpectralFlatness: [0x0 string] SpectralEntropy: [0x0 string] TFRidges: [0x0 string] InstantaneousBandwidth: [0x0 string] InstantaneousFrequency: [0x0 string] InstantaneousEnergy: [0x0 string] MeanEnvelopeEnergy: [0x0 string] TimeSpectrum: [0x0 string] WaveletEntropy: [0x0 string] ScaleSpectrum: [0x0 string] All: [0x0 string]
Scalar and Vector Features in Time-Frequency Domain
Set scalarization methods to convert time-frequency-domain feature vectors to scalar values.
Specify "Entropy"
and "Mean"
as scalarization methods for the spectral flatness feature. Specify "Kurtosis"
as the scalarization method for all the enabled signal features. Store this information in a timeFrequencyScalarFeatureOptions
object.
opts = timeFrequencyScalarFeatureOptions( ... SpectralFlatness=["Entropy" "Mean"], ... All="Kurtosis")
opts = timeFrequencyScalarFeatureOptions with properties: SpectralKurtosis: [0x0 string] SpectralSkewness: [0x0 string] SpectralCrest: [0x0 string] SpectralFlatness: ["Entropy" "Mean"] SpectralEntropy: [0x0 string] TFRidges: [0x0 string] InstantaneousBandwidth: [0x0 string] InstantaneousFrequency: [0x0 string] InstantaneousEnergy: [0x0 string] MeanEnvelopeEnergy: [0x0 string] TimeSpectrum: [0x0 string] WaveletEntropy: [0x0 string] ScaleSpectrum: [0x0 string] All: "Kurtosis"
Create a signalTimeFrequencyFeatureExtractor
object to extract the spectral crest, spectral flatness, and time-frequency ridges features. Use opts
to set the scalarization method property of the feature extractor object.
sFE = signalTimeFrequencyFeatureExtractor( ... SpectralCrest=true,SpectralFlatness=true, ... TFRidges=true,ScalarizationMethod=opts)
sFE = signalTimeFrequencyFeatureExtractor with properties: Properties FrameSize: [] FrameRate: [] SampleRate: [] IncompleteFrameRule: "drop" FeatureFormat: "matrix" Transform: "Spectrogram" ScalarizationMethod: [1x1 timeFrequencyScalarFeatureOptions] Enabled Features SpectralCrest, SpectralFlatness, TFRidges Disabled Features SpectralKurtosis, SpectralSkewness, SpectralEntropy, InstantaneousBandwidth, InstantaneousFrequency, MeanEnvelopeEnergy InstantaneousEnergy, WaveletEntropy, TimeSpectrum, ScaleSpectrum
Extract vectors and scalar features from the spectrogram of a signal. Observe the list of extracted features.
x = exp(-(-4.5:0.15:4.5).^2); [features,indices] = extract(sFE,x); disp(indices)
SpectralCrest: [1 2 3 4 5] SpectralCrestKurtosis: 6 SpectralFlatness: [7 8 9 10 11] SpectralFlatnessEntropy: 12 SpectralFlatnessMean: 13 SpectralFlatnessKurtosis: 14 TFRidges: [15 16 17 18 19] TFRidgesKurtosis: 20
More About
Scalarization Methods for Domain-Specific Signal Features
To set the scalarization methods for features in time domain, frequency domain, or time-frequency domain, select the domain-specific feature extractor objects and scalarization method specification. Refer to the following table for the list of domain-specific features from which you can extract scalar features.
Feature domain | Feature extractor object | Scalarization method specification | Features that support scalarization |
---|---|---|---|
Time | signalTimeFeatureExtractor | timeScalarFeatureOptions object | PeakValue |
Frequency | signalFrequencyFeatureExtractor | frequencyScalarFeatureOptions object | PeakAmplitude WelchPSD |
Time-frequency | signalTimeFrequencyFeatureExtractor | timeFrequencyScalarFeatureOptions object | All time-frequency features |
For a given feature vector v with N elements, the scalarization method options convert v to a scalar s as follows.
"Mean"
— Mean, defined as the average value of v."StandardDeviation"
— Standard deviation of the elements of v, normalized by N-1."PeakValue"
— Peak value, defined as the maximum absolute value of v."Kurtosis"
— Kurtosis, defined as the ratio between the fourth moment of v and the squared second moment of v."Skewness"
— Skewness, defined as the ratio between the third moment of v and the second moment of v raised to the power of 1.5.
"ClearanceFactor"
— Clearance factor, defined as the ratio between the peak value of v and the squared mean of the square roots of the absolute values of v."CrestFactor"
— Crest factor, defined as the ratio between the peak value of v and the root-mean-square value of v."Energy"
— Energy, defined as the sum of the squared values of v."Entropy"
— Entropy, defined as the sum of plog2p values, where p is the vector of normalized squared values of v with respect to their sum.where
Note
The scalarization method
"Entropy"
is not supported for theWaveletEntropy
nor theSpectralEntropy
features."ImpulseFactor"
— Impulse factor, defined as the ratio between the peak value of v and the average absolute value of v.
Version History
Introduced in R2024a
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