# Tag Info

Accepted

### Are IIR filters (and specifically Butterworth filter) causal?

Yes, Butterworth are IIR. The decay from an impulse technically lasts forever. Yes, all [implementable] IIR are causal. Yes, because of #1 and #2. Don't use ...
• 14.9k
Accepted

### Convert RGB Image to Grayscale and Display It (Python + Matplotlib)

You need to set the cmap properties of the imshow() function: https://matplotlib.org/devdocs/api/_as_gen/matplotlib.pyplot....
• 39.3k
Accepted

### Why is Scipy implementation of Hilbert() function different from Matlab implementation of the function?

It works fine for me: ...
• 14.9k
Accepted

### Designing digital low pass filter with low pass-band group delay

Minimum phase filters will not give you a near constant group delay. You can design a non-linear phase FIR filter with a linear desired passband phase with a specified group delay that is smaller than ...
• 79.2k
Accepted

### Calculating values of frequency bins in Python

This is simply how Discrete Fourier Transform (i.e. Fourier Transform theory applied on sampled signal) works. You get an output of length N if your input has ...
• 191
Accepted

### How to calculate the PSD from the complex calculated STFT?

I normally use the Welch method to calculate and plot the PSD of a signal. ...

### Why does a higher sampling frequency mess up my bandpass filter?

With an IIR filter, the higher the ratio is of sampling frequency to bandpass filter frequency, the closer the poles are to the complex unit circle in the Z-transform. Poles close to the unit circle ...
• 33.8k
Accepted

### Why does a higher sampling frequency mess up my bandpass filter?

As others said in the comments, this looks like numerical error. 3rd-order filters are not typically prone to this, but the higher your sampling frequency, the closer the poles move to +1: You might ...
• 14.9k
Accepted

### How to convert a spectrogram back to a signal

I am not a good Python coder, but did similar processing in Matlab in the past. The subject has been discussed in SE.DSP in several instances, for instance Librosa stft + istft - Understanding my ...
• 29.6k