extracting data from wavelet

can someone pls help me with the code to extract variance data from wavelet plot in matlab? like how to extract X variation data correspondig to a Y axis value from a wavelet.

thank you

Answer 1

[Suraj Kumar]

Hi Devi,

To extract variance data from a wavelet plot in MATLAB, we can start by computing the Continuous Wavelet Transform (CWT) of your signal using the `cwt` function. This function provides us with the wavelet coefficients and their corresponding frequencies or scales. Once we have these coefficients, we can identify the specific frequency that corresponds to the Y-axis value.

t = 0:0.001:1; 
signal = sin(2*pi*50*t) + sin(2*pi*120*t);
[coefficients, frequencies] = cwt(signal, 'amor', 1/t(2));
desiredFrequency = 50;
[~, freqIndex] = min(abs(frequencies - desiredFrequency));
desiredCoefficients = coefficients(freqIndex, :);

After identifying the relevant coefficients, we can calculate their variance using MATLAB's `var` function. This variance represents the variation in your signal at the specified frequency.

varianceValue = var(desiredCoefficients);
disp(['Variance at frequency ' num2str(desiredFrequency) ' Hz: ' num2str(varianceValue)]);

Variance at frequency 50 Hz: 0.9514

To learn more about the functions 'cwt' and 'var' in MATLAB, please refer to the following documentation links:

https://www.mathworks.com/help/wavelet/ref/cwt.html

https://www.mathworks.com/help/matlab/ref/double.var.html