# Questions tagged [smoothing]

Smoothing a signal or data set approximates the data to reveal patterns and exclude noise, fine-scale structure and rapid changing phenomina.

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### Choose the right Sigma for Gaussian filter

I have the following problem: I have a time series with counted data. I now want to smooth it using a Gaussian low-pass filter. Is there a method to determine the sigma value? The window should have a ...
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### Continuous time double exponential filtering in state space form?

I'm trying to determine the continuous time formulation of the double exponential filter so that I can adapt it more flexibly for my particular problem. Typically, this model is expressed as a pair ...
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### Following a smoothing filter of a biological signal

)Following a smoothing filter of a biological signal. y[n] = Ay[n − 1] + Bx[n − 2] Please find the transfer function in the z-domain and find the impulse response function of this filter.
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### Why should an image be blurred using a Gaussian Kernel before downsampling?

I recently read that before downsampling an image, it should be blurred using a Gaussian Kernel. This way, the downsampled image is better than just picking a single pixel out of a NxN block or ...
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### Smoothing a discrete function with point wise variances

In Stark's Introduction to numerical methods [1970] it suggests fitting local polynomials to smooth discrete data before the Fourier transform using least squares minimisation. This gives the ...
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### Selected bin oscilation in STFT

I am looking for a noisy signal using STFT. My window length is 128 and I am using 75% overlap. I am using a Hanning window before running the FFT process. I am using Quinn's 2nd estimator for ...
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### Smooth signal with Hanning

I have an acceleration record and i want to smooth it's spectrum by using a hanning window with Bandwidth=0.5 Hz. How could i do that? Example in python/matlab will be appreciated!
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### Issues with the smoothing operator in coherence estimation using the complex Morlet (Gabor) wavelet

The goal I wish to compute the coherence estimate using the continuous wavelet transform (CWT) of a real-valued signal with the complex Morlet (a.k.a. Gabor) wavelet. I compute the cwt of the signal ...
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### Error introduced by smoothing filter at the end of a processing block

I'm running analysis on a multichannel audio signal and due to the size have decided to process it in blocks (my computer doesn't have enough memory to process it in one go). Some of the data produced ...
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### How Can I Detect Peaks and Regions of Highest Variance in a 1D Signal?

I'm not a signal processing person at all so hopefully I'm not asking an obvious question (if I am, I'd appreciate any resources that would help give more context). I have a 1D vector where the ...
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### Savitzky-Golay smoothing filter for not equally spaced data

I have a signal that is measured at 100Hz and I need to apply the Savitzky-Golay smoothing filter on this signal. However, on closer inspection my signal is not measured at perfectly constant rate, ...
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### Effect of Gaussian Blur on Different Frequency Components of an Image

Gaussian blur is lowpass filter which means it pass the low frequency components and stop the high frequency component but the point I am not getting is that if it is lowpass filter then how it is ...
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### Filterpy Kalman Filter batch processing with multiple measurement sources

In pythons module for kalman-filtering, filterpy, there is a function batch_filter() to batch filter a list of measurements that then can be used for RTS-smoothing. ...
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### Can you predict how long a discontinuity will take to reach its target if it is low pass filtered at a certain frequency?

Let's say you have a signal that relatively slowly rises from 0 to 1, then suddenly from one sample to the next drops back to 0, creating a sharp discontinuity. Let's say you run it through a one pole ...
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### How to smooth (or interpolate) phase of FFT and reduce data points

I am writing some code for audio analysis, and have currently got two signals with FFT performed on them. I get the phase of my complex array by using: ...
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### Is there a technical term for this simple method of smoothing out a signal?

Firstly, I am new to DSP and have no real education in it, but I am developing an audio visualization program and I am representing an FFT array as vertical bars as in a typical frequency spectrum ...
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### Slew Rate Filter With Different Smoothing Factors in Each Direction

I'm smoothing the output of an ADC with a simple first order low pass filter. Of course the smoothing rate is the same whether the signal is rising or falling. Preferably the smoothing rate needs to ...
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### Smooth 2D Data with Discontinuous and Artificial Jumps

I have some data $(X,Y,Z)$, which is a set of measurements $Z$ over a $2D$ space $X$,$Y$. The $Z$ data on this space is continuous except for some discontinuous jumps in certain domains of $X$,$Y$ (...
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The highest voted answer to this question suggests that to denoise a signal while preserving sharp transitions one should minimize the objective function: $$|x-y|^2 + b|f(y)|$$ where $... 2answers 670 views ### Transfer function of double exponential smoothing? Double exponential smoothing a.k.a. Holt-Winters smoothing tracks level and trend of a time series in coupled IIRs:$\qquad$In:$Y_t$, t = 0 1 2 ...$\qquad$State:$L_t, T_t \quad$-- level and ... 0answers 88 views ### Algorithm for smoothing the output of an object detector operating on a video? Please could you point me towards an algorithm that takes a series of object detections performed on a frame by frame basis as input and outputs a filtered series of object detections in which the ... 2answers 5k views ### When should the sum of all elements of a gaussian kernel be zero? I found an approximation of a 5x5 2D convolution kernel like this : Here, the sum of the elements is zero and this one was used for Laplacian of Gaussian! Another one here : This one has all ... 0answers 95 views ### temporal smoothing: FWHM of Gaussian kernel vs. window length of moving average Suppose in one case I convolve Gaussian kernel with FWHM=10 samples. I would like to compare the result with moving average. My question: should I take the moving average window also 10 samples? In ... 0answers 52 views ### Difference Between a 1st Order SG Filter And a Least Squares Moving Average I have been studying SG filters and i recently found another filter which seem to be commonly used in financial data smoothing which is the least-squares moving average, this filter is also called ... 5answers 28k views ### Noise Removal from an Image Using OpenCV (Comparison to Neat Image) I tried removing noise from the image shown below using Median Blur in OpenCV. But i'm not able to remove the colour noise completely as it is done in Neat Image. Any suggestions.? 1. Original Input ... 2answers 314 views ### Filter for Reducing Background Noise in Image I have images where there is a lot of "black" background (few shades of black). (In many images at least half the pixels are background). I need to get interest points from the image, but because the ... 0answers 65 views ### Implementing Edge Preserving Diffusion (Anisotropic Diffusion) I am trying to implement edge preserving diffusion. Recall the general diffusion equation to be: $$\DeclareMathOperator{\Div}{div}\delta_t u = \Div(g \nabla u)$$ Where$g$is the speed of the ... 1answer 652 views ### How to extract a smooth contour from a set of points in 3D? I am trying to segment a 3D volume. The outcome of all my volume segmentation algorithms is a set of candidate points in 3D space. Now I need to smooth this point cloud and fit a closed surface it. My ... 2answers 4k views ### Generating smoothed versions of square wave, triangular, etc I'm trying to get functions depicting smoothed out versions of wave forms(triangle,square, sawtooth, reverse sawtooth) which have the same amplitude and frequency as$cos(x)\$. I found a few ...
I am using IIR filter for smoothing $$y[n] = ax[n]+(1-a)y[n-1]$$ My question is, if I add another IIR filter, will it be the second order of IIR filter? If not, what it can be called? My second ...