# 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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### MACE correlation filter - any suggested values of of u?

I am trying to understand the MACE correlation filter as per the paper Mahalanobis, A., Kumar, B.V.K.V., Casasent, D.: Minimum average correlation energy ﬁlters. Appl. Opt. 26, 3630–3633 (1987) ...
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### Need help understanding convolution indexing

Ok, this is leaving me increasingly frustrated. This builds on a previous question here but I am still not getting the indexing, although I learned from that question all the same. Case 1: First ...
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### minimum sampling rate for very short duration signals

I understand that sampling rate should be twice the signal bandwidth for successful reconstruction. But what I don't get is how this translates in the time domain. For example, I have a sine wave ...
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### Calculation of the correlation of two sinusoidals

First of all I apologize for the long question. I am working with a 3-axis accelerometer and a 3-axis gyroscope and I need to calculate the correlation between the different signals (acceleration in x,...
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### Evaluating auto correlation strength (Gamma)

I'm working on Cognitive Radio in TV Band Spectrum. I need to sense the presence of signal in a particular spectrum. I have to sample the incoming signal (say 1000 samples) and I have to find the ...
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### How do you find signal similarity when one signal has zero values? Correlation alternative?

I'm using cross-correlation to look for a Barker code in a BPSK signal. It occurred to me that if I send out a zero DC valued signal proceeding the barker code, it won't affect the correlation ...
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Let's say I have two images that are parts of the same bigger image, cut using two masks (for simplicity, let's assume that the masks are just rectangles of the same size). The images are presumed to ...
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### Normalized Square Error vs Pearson correlation as similarity measures of two signals

Which measure should be considered better and when ? I tested both the measures on some data that I have and I got mixed results i.e. some are showing better results with Pearson and some with the ...
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### Phase Correlation - Poor Performance on Noisy/Blurred Images?

I have successfully tested 1D phase correlation algorithm to determine vertical shift between two synthetic images. When I moved to real images, however, it is not able to detect translation at all (...
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### Phase Correlation and Negative Shifts

I am implementing phase correlation algorithm to determine shift between two images. It generally works, but I am not sure how to interpret the resulting shift. Pseudocode: ...
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### Calculating similarity between two signal plots

I have two plots, each having frequency as x-axis and Gain as y-axis. By taking one data set as a reference I have to calculate similarity between them. The graphs have same values on the x-axis and ...
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### Correlation between 2 functions

I have a periodical function $f(x)$ that is sampled in time, at a rate of 1 millisecond. Together with this, I also have a second function $t(x)$. I want to find the correlations between periods ...
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### Implement average as correlation

I have a MxN image matrix in, and need to get out matrix out size MxN as follows: Each point out[i,j] is the average of all in[i,j] inside a window size WxW (if boundary allows). For example if W=10 ...
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### Why do you get instantaneous phase by calculating correlation with a carrier signal?

I am somewhat new to DSP. I'm trying to implement BPSK by following this Python QAM tutorial. My code seems to work, but I really just ported the tutorial's Python code to C++, and do not understand ...
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### image correlation without fft

I want to stitch 2 images by crosscorrelation measure, but I don't want to use fft. I tryed this but something seems to be wrong.any suggestions? ...
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### Audio codec analysis in MATLAB: crosstalk

I am currently making an analysis of a codec system that can encode up to 2 wave files into 1 file and decode it. Here is a simple illustration: ...
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### Can FFT Substitute Correlation for This Case?

I'm trying to determine frequency of a repeating pattern in a time series. The sampling rate 100Hz and the pattern repeats itself with periods between 0.5 second and 1.25 second. This corresponds to a ...
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### Correlation filter output range normalization

I'm developing correlation filters based image recognition. I implemented MACE correlation filter in matlab: training code: ...
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### Matching delayed signals

I have pairs of 1d digitised waveform signals which are almost identical - except there are sections which are the same in both but one is delayed slightly. I need to find sections and the delay with ...
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### Component of one signal along the another

Whenever we need to find component of one signal along another signal we can do so by the help of dot product. I want to as if this method is valid for all kind of signals. Are there any restrictions ...