Questions tagged [signal-processing]

Digital signal processing of sound, video or other single or multidimensional data

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73 views

LowpassFilter and LeastSquaresFilterKernel implementation

I'm in the troublesome phase to port Mathematica code into another programming language. I cannot find a proper reference on the algorithm used in the ...
8
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3answers
1k views

high pass filter without losing detail

I have troubles doing a simple high pass filtering... Downloading the test data https://pastebin.com/74J8t2YV as "test.dat", you can see that overimposed on the signal there are some low frequencies ...
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0answers
105 views

Handling oscilloscope bitmap data

I'm using an oscilloscope from Tektronix; its output is formatted as a $n \times (m + 2)$ matrix, where $n$ is the number of vertical divisions and $m$ the temporal scale. The first $9\times 2$ ...
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75 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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1answer
148 views

Computing FundamentalFrequency

How does Mathematica use AudioLocalMeasurements to compute the fundamental frequency? Is there any formula? I can't seem to find what method Mathematica makes use ...
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1answer
564 views

How can I generate pink noise using Mathematica?

I need a time series of pink noise. How can I generate pink noise using Mathematica?
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1answer
110 views

Confused about the usage of AudioSpectralTransformation

The documentation for AudioSpectralTransformation says: AudioSpectralTransformation computes the short-time Fourier transform of audio, maps every value at ...
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1answer
64 views

Creating time varying 2d coordinates with OrnsteinUhlenbeckProcess

I see that I can create time varying 1d data with e.g. ...
2
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1answer
182 views

Implement inverse discrete-time Fourier transform

In Mathematica after version 9. We had ListFourierSequenceTransform to do discrete-time Fourier Transform, but we do not have the inverse function. If we peform it ...
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2answers
119 views

How to detect the singular value with wavelet analysis

I have a series data data=Uncompress[ FromCharacterCode[Flatten[ImageData[Import["http://i.stack.imgur.com/ApipY.png"], "Byte"]]]]; We can show it ...
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2answers
200 views

How to calculate the amount of offset about two list

You can get my data by this code {data1, data2} = Uncompress[FromCharacterCode@ Flatten[ImageData[Import["https://i.stack.imgur.com/ShSMY.png"], "Byte"]]]; We ...
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1answer
380 views

How to measure the pulse width in Plot Graph?

I'm practicing "Inverse Fourier transform" with impulse train using Diracdelta function. Condition Wavelength: 800(nm) Velocity of Lingt: 299,792,458(m/s) Using 1 and 2 >> Frequency0 = 299,792,458(...
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2answers
114 views

Can't get Mathematica to use FourierTransform in the way I want it to [closed]

I'm an EE working with signals and systems trying to get Mathematica to do a few basic functions to see if I could use it regularly in my work. Here's the code I'm working with: ...
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0answers
144 views

Manipulate Z-transform transfer function [closed]

I would like to express a Z-plane transfer function in a form of a difference equation so that I can implement it as an infinite impulse response filter. Here is an example of a continuous time ...
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173 views

Comparison of Continuous and discrete Fourier Transform

Consider a continuous signal as follows: ...
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1answer
67 views

Why am I getting unexpected result while implementing Fourier Transform?

I have considered five signals of different amplitude, frequency and phase components and applied Fourier Transform using the code given below: ...
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2answers
554 views

LowpassFilter Mathematica

I have this example signal: w1 = 3; (* rad/s *) w2 = 50; (* rad/s *) w3 = 4; (* rad/s *) signal[t_] = Sin[w1*t] + Sin[w2*t] - Sin[w3*t] I would filtrer this ...
3
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1answer
190 views

SAX implementation in Wolfram Mathematica

I have to deal with time series to find some patterns there. The method selected is SAX (based on PAA). There's a built-in function to convert a numeric times series into a series of letters with a ...
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0answers
105 views

How can I express chains of filters using recurrence relations?

Here's example of what I would typically do in Python to play around with system of custom filters: ...
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0answers
133 views

Challenge: Calulating The Resulting 2D Image Behind A Lens [closed]

This is a tough question! I would like to calculate how an image (a real 2D photograph) looks if I place a lens at a certain distance d1 from it and I observe it at a certain distance d2. It is ...
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1answer
102 views

Sum and dump operation

I've looked a different Mathematica functions, and I don't find the following: sum and dump. It would be: ...
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1answer
334 views

Fourier Transform accelerogram seismic

I have a seismic accelerogram. I tried to apply the Fourier Transform to interpolate function, but dosn't work. So, i applied the ...
2
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1answer
746 views

Finding peaks on a Periodogram

I am currently working on a school project involving modelling sound recordings of piano notes. I have used the periodogram function to graph my recording and would like to find the peaks of this ...
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2answers
861 views

How to get a smooth derivative graphic

You can get data by this code: data = Normal[Databin["fHVr7FSi"]] Visualize it like following We can find some non derivable ...
4
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1answer
212 views

Applying filters to data of the form {{x1,y1},{x2,y2},…}

When working with any kind of measurement data there is (at least) for me always a phase where I have to play around with different filters (such as MedianFilter, <...
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3answers
3k views

How to do deconvolution in spectrum with some peaks?

For example, I have the next spectrum: I've seen the next question ["How to perform a multi-peak fitting?"][2] but not answer to my question. I want deconvolution the spectrum to obtain three peaks (...
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1answer
142 views

Experimental Data Overlay/Fit

I have two different sets of data represented in Contourplots: As you can see, in different positions of space, both have these very characteristic sets of four peaks (2 blue and 2 yellow). What I ...
32
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3answers
5k views

Remove noise from data

Hi, as you can see above I have some experimental data which has a large offset and shows clear noise fluctations around the tendency of the curve. I wanted to ask if someone could suggest me a method ...
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2answers
290 views

How to detect discolorations in an image?

I'm evaluating the technical quality of an images and I'd like to scan it for defects from dirty sensors. Are there any filters to quickly detect a blob of discoloration? Here are a few examples:
3
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0answers
280 views

Whitening the data from the LIGO project

I'm following the official LIGO tutorial and I want to do a whitening process now. I computed FFT using hf=Fourier[data] then PSD using ...
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0answers
71 views

GW150914 gravitational wave detection incident analysis [duplicate]

I'm analyzing the data from LIGO project, about first detection of gravitational waves. In one of the many threads here, someone said when I want to do an ASD of the strain I should use ...
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2answers
296 views

Power spectrum density calulation with ARProcess

I have a measurement of $x$ coordinates of an oscillating particle at presence of noise taken at constant time steps of 1/60 s. The corresponding data set can be obtained here: https://drive....
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5answers
777 views

Why isn't LowPassFilter working for these parameters?

First I define a function, just a sum of a few sin waves at different angular frequencies: ...
4
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1answer
225 views

Identify a note in a song using Mathematica

I'm trying to figure out how to use Mathematica to identify a note from a song. The short .mp3 file found here or here contains a bass-note that I'd like to identify. I can find it through ...
3
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0answers
181 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 : ...
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2answers
405 views

Applying a window over a list

The window functions state that they tread over lists, but when I try to do: HammingWindow/@list, I do not get the expected results. What is the best way to apply a window over an arbitrary length ...
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1answer
756 views

Finding outliers in 2D and 3D numerical data

I'm working on dataset which isn't normally distributed.which contains three dimensions like cost, discount and profit I'm trying to find outliers in all these dimensions. I used z score to find ...
2
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0answers
205 views

FindPeaks error “ Expecting an image or graphics instead of”

I'm running Mathematica 10.3.1.0 on windows 7 Professional Sp.1 when I try to use FindPeaks I keep getting the following error, even when trying the example in the ...
2
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1answer
124 views

Problem with Sin and ListPlot

In order to produce a smooth sine wave (Sin) and visualize it (ListPlot), I seem to need a very high sample rate (much higher than Nyquist). I want to know if this is a artifact of ListPlot or Sin ...
1
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2answers
320 views

Plotting amplitude spectra of modulated message signal

I'm trying to plot the amplitude spectrum of the modulated message signal, I have managed to plot it by working through the maths, expanding out each trig function, and then drawing onto a graph ...
1
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1answer
89 views

Why there is a click sound when I play a sound?

When I consider this simple code: ListPlay[RandomReal[1, {2000}], SampleRate -> 1000] I hear a click at the beginning of the sound sample and at the end of ...
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0answers
107 views

Mapping the MATLAB SP Toolbox to Mathematica

We have some work and people where I am doing signal processing using the signal processing toolbox in MATLAB and it comes up how to translate one or another of the large number of functions in that ...
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0answers
197 views

Wavelet Data Visualization (modus and phase) ListPlot [closed]

Due to ContinuousWaveletTransform[...] I can obtain information about wavelet-coefficient for example ...
4
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1answer
782 views

Getting correct amplitudes with Periodogram

I'm having some trouble with the function Periodogram, mainly with getting it to produce correct amplitudes for the spectrum it returns. My question is how to fix ...
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0answers
139 views

Is oscillation seen in data signal or noise? [closed]

I have some experimental data which is well-fitted by 40 terms of a Fourier series. I want to know if the oscillation exhibited is signal or noise. I evaluated the code shown below to plot my data in ...
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0answers
309 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 ...
4
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0answers
345 views

Constructing the spectral density of white noise

My goal is to find the spectral density $S_{XX}(f)$ from a time domain noise signal $X(t)$. The approach should work for general time series, but to illustrate what I've been doing I'll keep it simple:...
14
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1answer
692 views

Extracting signal from gaussian noise

I am trying to extract a signal, $X$, from a noisy source of data, $Z$: $Z = X + Y$ where I know that $Y\sim N(0,\sigma)$, and I know the standard deviation $\sigma$. I am starting with a surrogate ...
2
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3answers
492 views

Using BandpassFilter

https://drive.google.com/file/d/0B7G3oUuZG1TwRHNNV1RFZjFWUXM/view?usp=sharing Above I have linked a data set containing a 2 seconds EEG sample I have recorded of someone "blinking". This data set was ...
6
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6answers
626 views

How do I build a patterned matrix (high-pass and/or low-pass filter bank)?

I would like the shortest code to build the following matrices, of arbitrary dimension $N$: A Low-Pass filter bank matrix is of the form $ \begin{bmatrix} 1 & 1 & 0 & ...