Questions tagged [signal-processing]

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

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63 views

Prevent running out of memory when doing SpectrogramArray?

I was using SpectrogramArray[Import@"myFile", 22050, 22050]to transfrom a piano mp3 file so that I can (probably?) generate a midi file from that mp3. The step size ...
6
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2answers
185 views

How to segment nuclei from a noisy image

(data can be downloaded from this link.) I am trying to segment and count nuclei in a noisy 3-D image stack and it is proving to be somewhat challenging. The strategy I could come up with requires ...
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2answers
135 views

Two-tone spectrogram

The default spectrogram command uses a single color and appears to just vary the saturation of the color to express intensity. So, for example, in the default implementation which looks like this: ...
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1answer
968 views

Detecting beat frequency using FFT

I wrote Mathematica FFT code that works for non-beat signals, eg. Sin[2*Pi/20*x] and more complicated but I can't obtain beat frequency of Sin[2*Pi*(10)*x] + Sin[2*Pi*(11)*x]. Also, what is general ...
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2answers
181 views

Plot cumulative distribution of a function

I want to calculate the probability $P(X\le-0.5)$. I have the probability density function $1/(\pi\sqrt{A^2 - x^2})$. $A$ is supposed to be the square root of noise power, $A = \sqrt{N_0}$, and so ...
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0answers
120 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 $\...
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0answers
107 views

wavelet fourier transform

I want to do wavelet Fourier transform of my data but I have few doubts in this. 1)first of all what is octive and voice command here when i am changing value according to that my plot is changing but ...
2
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1answer
694 views

Cut off frequency of low pass filter

I have a data here, I want to make sense of Lowpass filtering function in Mathematica.I do not fully understand units of cut off frequency in this option since the data is in frequency space. What I ...
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0answers
174 views

Analysis of the periodic data by the maximum entropy method

I am trying to get the frequency spectrum of periodic data. Since the data set is short, the outcome of the frequency peaks are not sharp enough for me to do further analysis. I know the spectrum can ...
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0answers
75 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 ...
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3answers
2k 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
111 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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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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1answer
162 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
644 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
113 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
196 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
125 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 ...
6
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2answers
211 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 ...
2
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1answer
420 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
117 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
187 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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186 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
707 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
193 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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110 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
134 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
106 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: ...
3
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1answer
352 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
803 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 ...
7
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2answers
1k 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
225 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, <...
3
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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 (...
4
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1answer
143 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 ...
35
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3answers
6k 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 ...
8
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2answers
294 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
294 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
73 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
306 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....
6
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5answers
859 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
252 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
186 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 : ...
0
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2answers
464 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 ...
8
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1answer
866 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
264 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
129 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
372 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
91 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 ...