Questions tagged [filtering]

Questions on filtering or selecting data based on certain criteria. This is to be used with primary tags such as list-manipulation, string-manipulation or signal-processing, with the primary tag indicating the specific use case.

34 questions with no upvoted or accepted answers
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8
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0answers
738 views

How to implement a Kalman Filter

Below I use low level code to reproduce the example of a Kalman Filter on pages 16-20 found here. First I create the data. ...
4
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0answers
114 views

How to remove circled noise from image

Consider a simplified example: noise ...
4
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0answers
550 views

Nonuniform Savitzky-Golay filter for smoothing and differentiation

The classical Savitzky-Golay filter works only with uniformly sampled data and currently we have at least two good implementations of it for Mathematica published on our site. But in many practical ...
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0answers
85 views

Select certain term containing some patterns and confusing pattern Alternatives in FreeQ

I am considering a function termsContain[func_,list_] which select in an expression func the terms containing the ones in the ...
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0answers
122 views

FIR filter and the relation between Sample rate and cut-off frequency

I have problem to unterstand the logic of the cut-off frequency of the FIR filter. Suppose my sample rate is 2MHz and I want to design a lowpass filter with a cut-off frequency 100Hz. What will be $\...
3
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0answers
187 views

Filtering in frequency domain

I'm trying to modify a transfer function in the frequency domain by filtering it with a Butterworth filter. For example, let's say my transfer function is of the form : ...
3
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0answers
262 views

Application of lowpass Butterworth filter

I'm trying to design a Butterworth lowpass filter with a cutoff frequency of So far what I did is ...
3
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0answers
42 views

commutative matching

I've been doing some work that results in the creation of hundreds or thousands of equations with the same answer. To prevent them from collapsing to their simple answers, each has been passed through ...
3
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0answers
56 views

What are all the elements of the expression returned by KalmanEstimator used for?

The first "Application" in the documentation for KalmanEstimator is copied below with additional variables for clarity. ...
2
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0answers
26 views

How to select a part from a list of text imported from the internet

I import a dataset from the internet like: data=Import["http://www.test.com", {"HTML", "XMLObject"}] The dataset looks like this: ...
2
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0answers
53 views

Performance of different Count patterns

The two pieces of code below are functionally equivalent, and I would have expected similar performance. (The only difference between the two is the form of the pattern used.) But the second piece of ...
2
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0answers
375 views

Butterworth Bandpass Filter

I am translating someone else's code which is written in matlab to mathematica. I need help to design a Butterworth bandpass filter in mathematica to filter a sine wave. the sine wave is generated ...
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0answers
157 views

Gradient Filter Function

I am trying to understand EXACTLY what the GradientFilter function in Mathematica is doing. As far as I can tell, it appears to be doing a convolution of a first derivative of a Gaussian with the ...
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0answers
28 views

Use of padding in GaussianFilter

I understand from the help that Padding->None is a valid option for GaussianFilter[] With a setting Padding->None, ...
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0answers
40 views

How to filter audio to get best results in correlation?

I am trying to recognise the alphabetical letters by saving some data of records of me and others saying each letter, then comparing a test audio not contained in the data to each letter using the ...
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2answers
70 views

Select one among multiple solutions that satisfies a certain condition and 3D Plot it with varying simulation values

My function is as follows: $$f(x)=ax^5+bx^4+cx^3+dx^2+ex+g=0$$ Since it does not generate an analytical solution, I tried to do a simulation exercise as follows. Simulation values: $a=-2$, $b=3$, $...
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0answers
43 views

How to get a directed graph of size N which is also a connected component?

I need to get graphs of size N, in which the whole graph is a connected component. In particular, I'm working with a Albert-Barabasi distribution, with k=2, and random directed edges. Right now I'm ...
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0answers
46 views

KalmanFilter fails

I want to use a Kalman filter to reduce the noise in a time series. The underlying process has no dynamic and therefore can be modeled as an AR(1) process like a random walk. ...
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0answers
59 views

How to negate a boolean selection criteria

I know how to select from a list using a boolean function: Select[list, MyFunctionQ] But I can't figure out how to negate this. I've tried ...
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0answers
214 views

How to filter data?

I work with this dataset: ...
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0answers
65 views

AirportData, GeoNearest and filtering data

I bought a Raspberry Pi, which introduced me to Mathematica, and I'm just diving in. I'm guessing my question is really a basic syntax question, but I don't know how to unravel it. I thought I would ...
1
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0answers
44 views

select data within a cylindrical space

I am facing a problem to select data from a list {Xn,Yn,Zn}. Now I need to select data with a criteria Xn^2+Yn^2=1. How to write ...
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0answers
111 views

ButterworthFilterModel consumes the memory too much

I have a simple filter which is a result of the these questions here and here. I have to use this filter in a Do loop but I found that this filter consume the ...
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0answers
24 views

How to select multi vectors with particular condition

I have a matrix as: a01={{225., 1, 2, 3, 4}, {225.5, 2, 3, 4, 5}, {226., 3, 4, 5, 6}, {226.5, 4,5,6,7}} And I want to choose head: ...
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0answers
31 views

Export XYZ matrix selecting positive Z data points in three files and keeping the matrix form

The following code saves XYZ points in a separated file but keeping the matrix shape. ...
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0answers
56 views

solving inside for loop and sorting x which are less than 3 and greater than -3 from the list

I give a simple function code here... Clear[a, x, t]; s = ParametricNDSolve[{x'[t] + a*x[t] == 0, x[0]==1}, x, {t, 0, 100}, {a}] y = x[1] /. s y[5] /. s I ...
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45 views

Scraping Images that are Directly Embedded in a Webpage or Dynamic?

I need to scrape URLs for photo albums like Flickr and Facebook for images from a certain event. I'm trying to use Import["link", "Images"], as shown at https://...
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0answers
63 views

Butterworth single pole, 5 Hz cut-off frequency on accelerometer data for single axis

I have read other posts here on using the Butterworth filter in Mathematica, however, I am having a hard time understanding the chain of functions and their parameters as applied to my case, and I am ...
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0answers
77 views

Numerical error or mistake when filtering using Fourier?

I am comparing the filtering method using a recurrence filter with filtering using Fourier. I think both methods should give the same answer but they differ by a small amount that could be numerical ...
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0answers
43 views

Shift z exponents in transfer function

I have calculated a transfer function for an IIR filter: (-0.0729597 + 0.0729597 z^2)/(0.854081 + 0.71172 z + 1. z^2) But it doesn't have the right exponents for z, as I would like them to start at z^...
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188 views

Filtering imported MNIST data

I am using the following to import MNIST Data: data = ExampleData[{"MachineLearning", "MNIST"}, "TrainingData"] How do I get just the data for specific digits e....
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0answers
85 views

Filtering word data nouns by subfield?

I am making string combinations using WordData and would like to filter all nouns that come from a specific professional specialization. For example, the nouns in ...
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0answers
322 views

Engineering spectral densities using filtered white noise

My goal is to create time-spectrum noise signals with spectral densities $S_{xx}(f)$ for pretty much arbitrary spectral densities (think white noise, lorentzian, $1/f$). In finding advice on how to do ...
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227 views

How does KalmanEstimator update the Kalman gain, process noise and state variable mean?

The first "Application" in the documentation for KalmanEstimator is copied below with additional variables for clarity. ...