Questions tagged [correlation]
Correlation or Cross-Correlation is a measure of similarity of two waveforms as a function of a time-lag applied to one of them.
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convolution vs correlation?
What is difference between convolution and correlation?In simple words or in a nut shell?
As far as i am able to study is that Convolution is a mathematical operation used to express the relation ...
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how can I calculate tine gap in different waves
I want, calculate the time gap between two signals .but that signal has frequently changed the frequency range. I want to combine with these two signal including phase shift I have a circuit for ...
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30 views
Does this make sense for cross-correlation in frequency domain?
If I have a signal A at 2 kHz and signal B mixed at 2 kHz + 3kHz, and then i take the FFT of them both, and then cross-correlate them many times, the 3kHz peak should disappear? Since this peak is not ...
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39 views
How to verify if my cross-correlation algorithm works?
So I have a signal generator which can produce two separate signals.
I use a spectrum analyzer to read these signals, and can interface with Python.
I wrote a Python code which takes in these two ...
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How to extract information about each constituent 'wave' of a signal?
I have a vector containing wind speeds sampled at 1Hz over ten minutes.
I have applied a lowpass filter of 0.25Hz to get only the wind speeds I am interested in.
I now want to use MATLAB to ...
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18 views
How can I get better results from Phase Correlation
I am using Phase Correlation to register 3D data. There's a clear distinction in the y direction so the resulting shifts seem to be correct. But since there is a lot of similarity in the x direction ...
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Understanding correlation in image processing using examples
I have been trying to understand the intuition behind the correlation. I understand from this guide that correlation is a way to detect a known waveform in a noisy background. I have seen from this SO ...
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129 views
What is the time reversal convolution
Given a signal $r(t)$ which is a result of convolution between signal $x(t)$ and a channel $h(t)$ as below :
$r(t) = h(t)*x(t); $
what I know, the time reversal convolution can be process as ...
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16 views
Pearson correlation coefficient vs mutual information
I recently computed both the pearson coefficient and the mutual information of two time series as well as the corresponding error bars, and what I find out in the end is a significant level of ...
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Are there methods to measure how the change in one signal will affect another signal?
I have two distinct signals and I would like to compute their correlation. However, I think that just computing the crosscorrelation does not work here, since the signals are from different sources — ...
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21 views
Decorrelation for Adaptive Feedback Cancellation: How does it work?
I am going through lecture slides on adaptive feedback cancellation right now, and several decorrelation measures are mentioned.
As I understand, these are important in order to avoid a bias in filter ...
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38 views
Find repeating sequences in audio file
I have a long audio file (12+ hours). I know that there are some unknown small (2 minutes each or thereabout, it varies) repeating (not bit by bit: it is recorded with a mic) chunks in it, repeating ...
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122 views
Correlation of independent random processes
Suppose $X(t)$ and $Y(t)$ be two independent random processes. Is $E(X(t_1)Y(t_2))$ necessarily zero?
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70 views
Validating Jakes model in Rayleigh Fading channels
I am trying to validate the Jakes model by comparing the autocorrelation function given by $ \rho(\Delta t ) = J_{0}(2 \pi f_{d} \Delta t)$, where $ f_{d} $ is the maximum Doppler shift, $ J_{0} $ is ...
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93 views
What is definition of independent random variable
I wan't to ask that if
E{X}=0
E{Y}=0
and E{XY}=0
then how can I verify if the two random variables are independent or not.
X , Y are both continuous random variables {I am not able to recall ...
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224 views
Maximum cross-correlation coefficient value for time delay estimation
I am using cross-correlation for time delay estimation of two synchronized recordings ($x_1$ and $x_2$) of a fixed sound source from two different locations.
I understand that the delay is associated ...
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1answer
34 views
high & low pass correlated dither noise question
I read a pretty cool article the other day:
https://www.digido.com/ufaqs/dither-noise-probability-density-explained/
It says that if you have two dice (A and B) that you can roll both dice and then......
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Combine correlating input signals to generate multiple output signals
Choosing a descriptive title was quite hard, as I am not sure how to describe my problem accurately.
I have a mechanical system fitted with several sensors (Strain Gauges and motion Sensors). There ...
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39 views
How can i calculate a matrix of correlation?
I want to implement my own music algorithm detecting an angle of arrival of non-stationary signal and I need to make a matrix of correlation of this signal. I have problem because I don't know how to ...
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1answer
15 views
Can somebody explain SDF and MACE to me?
I can't find any information on SDF and MACE save for a vague exert in Kinser's Image Operators books. Therefore I am dumbfounded. I can't understand what they do and what's their role in composite ...
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69 views
Signals Cross Correlation from Their Power Spectral Densities?
For two real valued signals $f$ and $g$ with their corresponding power spectral densities $|F(k)|^2$ and $|G(k)|^2$ Is there a way to get an intuition of how correlated $f$ and $g$ are just by looking ...
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159 views
Cross Correlation, how can any signals except the trivial cases be uncorrelated?
I have been working on a problem where I am trying to subtract two Power Spectral Densities (PSD's) from one another in the following way. $$|F(k) - G(k)|^2 = |F(k)|^2 - |G(k)|^2$$
Which is only ...
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85 views
What kind of power spectrum implies uncorrelation in time?
I am new in signal processing field, and actually I just need some basic tools for what I am working on. I've learnt that the autocorrelation function is the inverse Fourier transform of the signal's ...
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33 views
Aperiodic Correlation function using FFT Method
Periodic correlation function between two binary sequences say x and y can be computed using FFT. corr_value = ifft(fft(x).*conj(fft(y));
Can some one please help on how to compute aperiodic ...
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Why is correlation involved? - Axis Rescaling for a 2D axes - brightfield illumination microscopy of blood cells
for 1D axis rescaling, you use a FOV calculation
len_pixel=total_magnification * len_specimen_in_pixel
len_specimen_in_pixel=len_pixel/total_magnification
and then to get the axes rescaled, you do ...
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59 views
Time delay estimation of signals increasingly decorrelated
The problem may be summarized as follows: I have a stochastic signals and I want to measure an increasing delay, as depicted in the following picture. The picture represents the signal as it is being ...
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150 views
What is the Fastest Way Ever to Do 2D Correlation?
Here is what i gathered so far:
Any sliding window classification, image filtering or similar can be fastly done by a FFT (flip the signal and do convolution).
Also, if the template/filter kernel is ...
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2answers
69 views
What is the betwwen [i,j] and [u,v] in explinations of correlation and convolution (picture attached)?
I don't know how to write 'summation' symbol here hence posting the picture.
Can someone explain to me the difference between i,j and u,v in this explanation of correlation and convolution?
I know ...
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1answer
74 views
Efficient correlation of a low duty cycle training sequence
Is there a way to efficiently correlate a training sequence that is N samples long, framed at M samples where M >> N, with L occurrences of such frames (see below). For the pedants, the training ...
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108 views
What is the difference between using corrcoef to compare two signals by column, and as whole matrices?
I have two matrices, which represent acceleration readings of the same event from two seperate sensors, and I would like to calculate the correlation coefficients so that I may get a measure of how ...
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192 views
How to get the background noise of microphone?
I am working on the automatic volume control for television which should take care of background noise. For this, I need to first find out the background noise. I have read in research papers that we ...
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73 views
Detection complex vectors by using correlation
I sent out a complex vector $x_i \in \{x_1,...x_n \}$ and receive a vector $y$.
I use correlation $y^Hx_i$ to detect which $i$ was sent.
If $y$ is corrupted by AWGN channel, the optimum rule should ...
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46 views
Co-prediction of signals
Is there any plausible method to estimate or predict one signal, on the basis of known value of another signal, provided the two signals bear a strong correlation?
For instance, the audio amplitude ...
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Physical interpretation of 4th-order correlations
BACKGROUND:
Let's say we have samples of a random process $X(t)$ at two different times, $t_1$ and $t_2$, denoted $X(t_1), X(t_2)$. The values of $X(t)$ represent some voltage-like quantity (i.e. a ...
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93 views
Two different definitions of cross-correlation
I have come across two different definitions of the cross-correlation function:
$$
R_{XY}(\tau) = \int_{-\infty}^{+\infty} x(t) y(t+ \tau) dt
$$
and
$$
R_{XY}(\tau) = \int_{-\infty}^{+\infty} x(t)...
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How can faux correlated data be generated for testing or training?
There are one or two questions here that ask how to assess data correlation. The data tends to be empirical.
Is there some tool or standardised technique for generating correlated data from scratch? ...
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82 views
What level of correlation coefficient suggests correlation?
In Python (and Numpy), I recently did:-
a = np.random.randint(0,256,1000)
b = np.random.randint(0,256,1000)
and when I calculate the correlation coefficient $r$ ...
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2answers
61 views
How to interpret correlation angle from frequency domain
Since the coefficient of one frequency could be seen the length of the signal projects on that frequency basis.
And the length is
$$|a|\cos\theta= \frac{a\cdot b}{|b|} $$
If I divide the ...
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1answer
140 views
Correlation of a signal
I have one sample for a signal. This sample is a vector of length 384. I need to calculate the correlation matrix for this signal,So I need many samples for the same signal.
How can i generate these ...
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1answer
98 views
Correlation between slightly misaligned images
I am matching camera images of projection screens with rendered pages of PDF documents using Pearson's and Spearman's correlation coefficient. When the images (3, 4, 5) are aligned, this works fine in ...
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1answer
46 views
BER performance of fractional equalizers for colored noise
I am trying to compare the BER performance of fractional and symbol spaced equalizers for channel equalization in colored noise scenario. I have found from simulation that for positively correlated ...
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1answer
35 views
How we can show that 2 correlated videos are similar?
Can I tell that different versions of the same video are correlated to each other?
and if so, how can I show this correlation? for example,
high-quality and poor-quality versions of the same video.
...
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1answer
431 views
Matrix cross correlation in python
I'm currently performing matrix cross correlation in python using :
C = scipy.signal.correlate2d(A,A)
where A is a 2D matrix, typically a picture. As you can ...
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1answer
195 views
Correlation Performed by Convolution
Background: The question here is related to images in particular and not signal/waveforms.
I have been reading a lot of answers about the difference between convolution and correlation but I am stuck ...
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2answers
683 views
How can I align these two signals? Cross correlation isn't working properly
I have two radios sampling simultaneously, and I am trying to time-align their two signals (they will always start sampling at slightly different times with random delays due to hardware differences). ...
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2answers
321 views
How can I synchronize signal from an LED and TTL pulses better?
I would like to synchronize my video and voltage data using Python. (I obtain these data using Bonsai and Open Ephys for an open field exploration experiment.)
I sent $150\text{ ms}$ long TTL pulses ...
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145 views
Calculation of Correlation Matrix
In the description of any Beamforming Technique for microphone array signal processing there is a usage of the co-relation matrix.
What is the use of calculating such a co-relation matrix in such ...
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1answer
26 views
Investigating correlation for unequal signal lengths
I have measurements from two tablet sensors. The first sensor measures the touch pressure applied to the tablet and the second sensor is the acceleration of the tablet (in z direction). The sensor ...
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1answer
270 views
Designing an efficient curve-matching algorithm
I'm currently designing a curve-matching algorithm and as I already explored many ideas I'm requesting your help. So, if you got some advices about how to handle this problem, feel free to answer!
...
