# 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.

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### 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. ...
118 views

### How to remove circled noise from image

Consider a simplified example: noise ...
133 views

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### 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. ...
67 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 ...
265 views

### How to filter data?

I work with this dataset: ...
71 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 ...
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 ...
114 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 ...
79 views

### Getting the primes in the range from 2 to 30

Why doesn't this get the primes in Range[2, 30]? ...
22 views

### Return Link with XML Element

I am trying to import multiple links. I just want the link after ...
19 views

### Identifying which polynomials from a list are factors of other polynomials

I have a list of integer polynomials $c_i(x)$ given by s = Table[c[i,x],{i,1,N}] for some large $N$. These polynomials are increasing in degree. I am trying to ...
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### 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. ...
61 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 ...
54 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://...
89 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 ...
86 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 ...
45 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^...
198 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....
86 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 ...
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 ...