# Questions tagged [scipy]

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### Welch method implementation not smooth

I have been trying to recreate the welch method implemented in scipy.signal by hand but my results don't look close enough in my opinion. How come the scipy.signal.welch method is displaying much ...
1 vote
80 views

### reproduce Scipy's stft

I failed to reproduce Scipy's stft. When I have tried to remove all the possible modifications and go the minimal example, I converge to the following: ...
• 1,084
72 views

### Numerical issues in scipy's Savitzky Golay filter coefficients for large polynomial order

Consider the design of a Savitzky-Golay filter of window length 101 and (high) polynomial order 20. Using scipy version 1.10.1, the filter coefficients can be obtained in python as: ...
• 375
1 vote
162 views

### How to construct a bandpass filter with minimal loss in amplitude/power near the lower and upper frequency limit in Python?

I am analyzing functional MRI data with a sampling rate of 1 second (1 Hz). The frequency band that I am interested in is 0.01-0.2 Hz. Regarding measurements, I am interested in computing (1) the ...
• 113
1 vote
98 views

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919 views

### Why does scipy introduce its own convention for H(z) coefficients?

Conventionally, the definition of the system function for a IIR digital system is: $$H(z)=\frac{b_{0}+b_{1}z^{-1}+b_{2}z^{-2}+\cdots}{1-a_{1}z^{-1}-a_{2}z^{-2}-\cdots}$$ where coefficients are the ...
• 433
653 views

### Why is implementing a digital LPF with low cutoff frequency but high sampling frequency infeasible?

I am new to signal processing and I want to implement an LPF using SciPy. In order to do so, I used the following python code from: here The code itself looks like: ...
• 53
1 vote
203 views

### Filtering with scipy sosfiltfilt generates flat edge artifact

I need to filter some array of data before differentiating it, I do this so I don't drown the signal in noise. It's also important that no delay is applied to the signal, that's why I decided to use a ...
• 29
90 views

### Initial conditions of backward filter for forward-backward filtering on chunked real data in python

I have to apply a downsampling filter on a realtime data stream (signal) and I want to do it in python. The data is sampled at 16 kHz and loaded in a loop in chunks of 1 second. I have to downsample ...
• 31
1 vote
607 views

### Scipy and Matlab Spectrogram not matching

I am trying to replicate a spectrogram from MATLAB in Python. I've read other posts but they either don't use complex data or the data doesn't match between languages. I've defined my FFT length (<...
385 views

### Scipy filter analog vs. digital

It would be greatly appreciated if the usage of the python package scipy's filter (e.g. butter) analog=True argument could be explained. I don't understand what is meant by this (any signal being ...
• 223
1 vote
135 views

### using scipy.signal.sosfilt to filter a stereo signal with zi, zf

I'm stuck trying to filter a two-channel signal using sosfilt() with the zi initial state. I need to use the zi parameter so I can carry the filter state over ...
692 views

### Amplitude extraction using STFT

I'm trying to recover amplitude/magnitude from an audio stream. I'm using FFT to go from time domain to frequency. If I feed in a signal of known amplitude, the results I get from either windowing or ...
• 243
319 views

### python how to demodulate iq fm signal that was moved to 0 frequency

I am struggling with implementing FM demodulation for IQ samples that has 0 center frequency from RTL-SDR ... I have found the following algorithm for FM demodulation, see FM demodulation: ...
• 101
15 views

### Extract PVC feature from singal to train the ML model with PVC characteristics

I have ML model which is trained on Afib, Normal, Other - 3 class. Currently when I am testing the model with unseen database, sometimes it identify PVC singals as Afib class. For example - enter ...
1 vote
138 views

### Possible error when finding group/phase delay in scipy

After designing a "least square optimal" FIR filter I wanted to find the group/phase delay, defined as: $P(\omega) \triangleq - \frac{\Theta(\omega)}{\omega}$ (Depending on the literature ...
• 13
206 views

### find out ideal window size for coherence analysis - python

Is there a general formula I could use to calculate the ideal window for the window argument in the function ...
• 133
337 views

### Signal Reconstruction Using Scipy.signal.cwt

Can someone explain to me how I can reconstruct a signal using the scipy.signal.morlet2? The codes in the link only allows one to do a fourier transform using the morlet wavelet, but there is no such ...
1 vote
38 views

### Convert MUSIC algorithm to EV

I write some code, but result looks very strange: ...
1 vote
94 views

### Prony method doesn't work

I have used the code from: https://github.com/quantumlib/OpenFermion/blob/v1.5.1/src/openfermion/linalg/wave_fitting.py#L41-L76 try using with my signal: ...
63 views

### Why is DFT magnitude less than expected?

Code for signal: ...
225 views

### scipy convolve and fftconvolve return different output [closed]

I'm writing an autocorrelation function using and I noticed a difference between fftconvolve and convolve that should use fft if it's faster. This is my function with convolve: ...
• 131
256 views

### Vectorizing a biquad filter (python / numpy)

I'm having a lot of fun writing signal processing code in Python / numpy, and I'm resisting the urge to pre-optimize the code. But my biquad implementation is slower than I want. Here's the inner ...
525 views

### How to convert between 2d convolution and 2d cross-correlation?

I am using cross-correlation for the purposes of image stabilisation. The images which I'm processing can sometimes be rather large. The contents of the image are often repeating patterns. For these ...
1 vote
435 views

### detrend a signal with break point but without jumps

Yesterday I asked a question and got the answer to detrend my time series which I think is really better than applying a highpass filter. So I read the description of scipy.signal.detrend and there I ...
1k views

### filtering EEG data with scipy.signal

I have EEG data recorded with a sampling rate of 256 Hz. Each recording contains 19 EEG channels. Other channels (like ECG data) are ignored. The recordings of 10 patients are 20 minutes long each, ...
1 vote
794 views

### How to generate a first order Gauss-Markov process in Python

I would like to synthesize a first order Gauss-Markov process from a white Gaussian noise. I know from signal processing theory that it could be realized using a noise shaping filter designed properly ...
• 11
378 views

### How to get scipy remez to give matlab firpm answer?

If I run this in matlab: h = firpm(100,[0 0.1 0.2 1],[0 0 1 1]) and this in scipy: h = remez(100,[0, 0.05, 0.1, 0.5],[0, 1]) I ...
• 141
1 vote
1k views

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