Questions tagged [scipy]
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192
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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:
...
- 1,072
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1
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62
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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:
...
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2
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115
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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 ...
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74
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3
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2
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886
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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
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596
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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:
...
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146
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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 ...
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64
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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 ...
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2
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446
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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 (<...
- 131
4
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347
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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 ...
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99
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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 ...
- 185
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2
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484
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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
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204
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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
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0
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14
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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 ...
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2
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120
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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 ...
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155
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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 ...
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228
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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 ...
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37
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1
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80
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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:
...
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63
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2
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1
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175
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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:
...
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212
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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 ...
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381
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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 ...
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1
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343
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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 ...
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1
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841
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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, ...
- 153
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642
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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 ...
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336
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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 ...
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2
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995
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Rolling average in pandas using a Gaussian window
I want to estimate the rolling average of a time series B using a Gaussian window. The equation to do this would correspond to
$$\tilde{B_{s}}(t_{n}) = \frac{1}{A_{s}} \sum_{t_{m}= t_{n}-3s}^{t_{n}+3s}...
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253
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Jerk detection in accelerometer data
I want to detect jerk from accelerator data i.e. values beyond 1.57 m/s^2, but due to the high frequency nature of the sensor (400 values per second), it gives multiple jerks instead of one.
How can I ...
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1
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2
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326
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Constraints on number of taps in a FIR filter vs. FFT length
I want to implement a FIR highpass filter for acoustic signals.
I generate the FIR using Python's SciPy code:
...
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337
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Why does Python welch give me a different answer from MATLAB's pwelch?
I am trying to implement the following line of MATLAB code:
[pxx, f] = pwelch(data,[],[],4096,F_S)
in Python. Knowing that MATLAB using a Hamming window type that ...
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463
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How does SciPy's Welch function change the shape of the data?
I am working with some time series data with a shape of 8064. The data is actually the popular EEG data called DEAP. It basically is a 3D array of size (40, 40, 8064) and here is the link to the ...
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75
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Decimate a signal whose values are calculated, not stored
tl;dr I'm looking for something like Scipy's decimate function, but one that takes in a generator, rather than a Numpy array.
I am turning on and off a light using ...
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2
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342
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Why does changing the format of an audio file from int16 to float produce jitter?
I read an audio file (an instrumental music file that is mono and 16000) with wav.read (read function from scipy.io.wavfile.) This function gives me a data file in int16 format. When I change the type ...
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119
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Understanding FFT bins interpretability
I am familiar with the continuous Fourier transform yet the more I try to understand FFT, the more I'm confused. If we've got a discrete N sample signal, FFT is a faster way to calculate DFT. If ...
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633
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(Python - Scipy - Wave files) Can a float signal be written with values higher than 1?
While developing an application, I noticed strange behaviour while using scipy.io.wavfile to write audio files. The documentation says that floating-point data is written within a range between -1 and ...
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270
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Simulation of Lock-In Amplification in Python makes no sense
I would like to simulate a basic lock-in amplification for post-processing some data. I wrote a basic Python script for this purpose but the output of the lock-in amplification does not seem to make ...
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463
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Spectrogram of x,y,z data from accelerometer
Using scipy.signal.spectrogram for creating spectrogram and matplotlib's pcolormesh for plotting.
I'm working on a project where I'm using a spectrogram to visualize the frequencies of the ...
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170
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How to determine multiple Periodicities present in Timeseries data?
My objective is to detect all kinds of seasonalities and their time periods that are present in a timeseries waveform.
I'm currently using the following dataset:
https://www.kaggle.com/rakannimer/air-...
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How can to obtain the transfer function of a bandpass digital filter? [duplicate]
I've been asked to: create a bandpass filter amplifier in python, determine the transfer function, graph the bode diagram, and print the highcut frequency, lowcut frequency, the bode constant and the ...
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153
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Fast Fourier transformation of discrete linear line function in Python using scipy.fft [closed]
Consider a time series dataset generated by a linear function
$$y = a \cdot n, \; n=0,1,...,N$$
According to this reference (entry 308 in the table for one-dimensional functions), the analytical ...
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Creating 60s strips from ecg signal recording ( .bat ) file and give it a label as per the datapoint present in it
I am working with https://physionet.org/content/mitdb/1.0.0/ dataset where we have 48 ecg signal files.
Each recording is 30 minutes long and I Want to create 60s strips and give it a label. ie based ...
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Scipy tf2zpk doesn't return zeros
I have the following transfer function:
$$H(z) =\frac{\alpha z}{(z-(1-\alpha))}$$
I'd like to find zeros and poles of it by scipy.signal.tf2zpk:
...
- 345
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965
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How to set the "widths" parameter for continuous wavelet transform using Morlet wavelets? (scipy.signal.cwt)
I'm trying to use scipy.signal.cwt() to do a time-frequency decomposition of neural data. However, I don't completely understand the "widths" parameter.
I ...
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Help on audio filter with FFT on python
I need to take a .wav audio file that's noisy and filter out some noise. I have to do it using Fourier Transform. After some days researching and experimenting, I finally made a working function, the ...
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121
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0
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293
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Remez function equivalency between Matlab and Scipy
I've read the similar question Find the equivalent of this python remez specs in C++ remez or Matlab firpm, which describes a different problem.
In Matlab, I have following ...
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2
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1k
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How to implement cascaded biquad transfer functions in Python/SciPy
I am trying to implement in python/Scipy the biquad filter with the following S-domain transfer function:
$$
H(s)=\frac{w_0^{2N-1}(s+w_z)}{[s^2+(w_0/Q)s+w_0^2]^N}
$$
My problem here is that because of ...
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462
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Why doesn't the convolution of the impulse response match the system's output?
If you define an LTI system sys in scipy, you may conveniently feed an input x to it to get ...
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Can someone explain why signal.freqz() generates a different phase in the frequency fresponse than scipy.signal.dfreqresp()?
I have been using scipy to analyze filter performance for a single-pole IIR filter, and I noticed a disagreement between the phase in the outputs of the freqz() function compared to the output of the ...
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