generateMATLABFunction

Create MATLAB function compatible with C/C++ code generation

Since R2021b

Syntax

generateMATLABFunction(sFE)

Description

generateMATLABFunction(sFE) generates code based on the input feature extractor object sFE and opens an untitled file containing the function extractSignalFeatures. The function signature depends on how you set the FeatureFormat property of the input feature extractor object.

• When you specify FeatureFormat as "matrix", the generated MATLAB^® function has this signature:

  [features,info,framelimits] = extractSignalFeatures(x)

  The signature is equivalent to:

  [features,info,framelimits] = extract(sFE,x)

• When you specify FeatureFormat as "table", the generated MATLAB function has this signature:

  features = extractSignalFeatures(x)

  The signature is equivalent to:

  features = extract(sFE,x)

Examples

Generate Equivalent MATLAB Function for Feature Extraction

Create a signalTimeFeatureExtractor object to extract the mean, standard deviation, and peak value of a random signal.

x = randn(1000,1);
sFE = signalTimeFeatureExtractor(FrameSize=100, ...
      FrameOverlapLength=10,Mean=true,StandardDeviation=true, ...
      PeakValue=true)

sFE =
   signalTimeFeatureExtractor with properties:

    Properties
               FrameSize: 100
      FrameOverlapLength: 10
              SampleRate: []
     IncompleteFrameRule: "drop"
           FeatureFormat: "matrix"

    Enabled Features
      Mean, StandardDeviation, PeakValue

    Disabled Features
      RMS, ShapeFactor, SNR, THD, SINAD, CrestFactor
      ClearanceFactor, ImpulseFactor

Call generateMATLABFunction on the object. The generated function extractSignalFeatures is equivalent to calling the extract function on sFE. Save the function to your current folder and view the function script.

generateMATLABFunction(sFE)
type extractSignalFeatures

function [features,info,frameLimits] = extractSignalFeatures(x)
% EXTRACTSIGNALFEATURES Extract signal features
% [FEATURES,INFO,FRAMELIMITS] = extractSignalFeatures(X) returns a matrix
% containing features extracted from input X, INFO, a structure that maps
% a specific feature to its column location in the output feature matrix
% and FRAMELIMITS, whose i-th row contains the beginning and end limits
% of the i-th frame.
%
% Parameters of the signalTimeFeatureExtractor used to generate this
% function must be honored when calling this function.

% Generated by MATLAB(R) 9.11 and Signal Processing Toolbox 8.7.
% Generated on: 10-Jun-2021 08:25:02.

%#codegen

if istimetable(x)
     xInTT = x{:,:};
else
     xInTT = x;
end
if isrow(xInTT)
     xIn = xInTT(:);
else
     xIn = xInTT;
end
dataType = class(xIn);
signalLength = size(xIn,1);
numChannels = size(xIn,2);
frameSize = 100;
frameOverlapLength = 10;
frameRate = frameSize - frameOverlapLength;
featureMatrix = zeros(0,1,dataType);
numFeatureCols = 0;
numFeatureRows = 0;
frameLimits = zeros(0,2,dataType);
info = struct('Mean',0,'StandardDeviation',0,'PeakValue',0);
for idx = 1:numChannels
    if numChannels == 1
         xChannel = xIn;
    else
         xChannel = xIn(:,idx);
    end
    startIdx = 1;
    endIdx = frameSize;
    while startIdx <= signalLength
        if endIdx > signalLength
            break;
        end
        featureIndex = 1;
        xFrame = xChannel(startIdx:endIdx,1);
        meanValue = mean(xFrame);
        numCurrentFeature = numel(meanValue);
        info.Mean = featureIndex;
        featureIndex = featureIndex+numCurrentFeature;

        standardDeviation = std(xFrame);
        numCurrentFeature = numel(standardDeviation);
        info.StandardDeviation = featureIndex;
        featureIndex = featureIndex+numCurrentFeature;

        peakValue = max(abs(xFrame));
        info.PeakValue = featureIndex;

        featureVector = [meanValue(:);standardDeviation(:);peakValue(:)];
        featureMatrix = [featureMatrix;featureVector];
        if startIdx == 1
            numFeatureCols = size(featureVector,1);
        end
        if idx == 1
            numFeatureRows = numFeatureRows+1;
            frameLimits = [frameLimits;[startIdx endIdx]];
        end
        startIdx = startIdx+frameRate;
        endIdx = startIdx+frameSize-1;
    end
end
tempFeatureMatrix = reshape(featureMatrix,numFeatureCols,numFeatureRows,numChannels);
features = permute(tempFeatureMatrix,[2,1,3]);
end

You can replace calls to extract with calls to the generated function in your code. The outputs are identical.

features1 = extract(sFE,x)

features1 = 11x3
      0.0842    1.0690    2.7526
      0.0500    1.0516    2.9491
      0.1901    1.0356    2.7304
      0.1209    0.9171    2.4366
      0.0443    0.9399    2.4247
     -0.1153    1.0490    3.5699
     -0.1001    0.9530    2.4124
      0.0616    0.9959    2.7485
     -0.0263    0.9482    2.4868
     -0.0234    0.9876    3.1585
        .
        .
        .

features2 = extractSignalFeatures(x)

features2 = 11x3
      0.0842    1.0690    2.7526
      0.0500    1.0516    2.9491
      0.1901    1.0356    2.7304
      0.1209    0.9171    2.4366
      0.0443    0.9399    2.4247
     -0.1153    1.0490    3.5699
     -0.1001    0.9530    2.4124
      0.0616    0.9959    2.7485
     -0.0263    0.9482    2.4868
     -0.0234    0.9876    3.1585
        .
        .
        .

Copyright 2020 The MathWorks, Inc.

Input Arguments

sFE — Feature extractor object

signalFrequencyFeatureExtractor object | signalTimeFeatureExtractor object | signalTimeFrequencyFeatureExtractor object

Feature extractor object, specified as a signalFrequencyFeatureExtractor object, a signalTimeFeatureExtractor object, or a signalTimeFrequencyFeatureExtractor object.

Version History

Introduced in R2021b