Questions tagged [cross-correlation]

A measure of correlation between different time series, at the same or different times.

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4k views

How can I estimate the delay between two non-periodic time series?

I'm wondering what the best way to estimate the delay and confidence between two non-periodic time series would be. Specifically, I thought it would be interesting to look at the different economic ...
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774 views

Why and when stationarity is achieved by decomposition rather than differencing in ARIMA model

I would like to understand relationships between variables by which cross-correlation function, that means what is the extent one variable influence the other one. ARMA model is used to fit two ...
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2answers
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Coefficient for a zero lag cross-correlation different from Pearson correlation r

Reading around I understood that using a cross correlation with lag zero should give the same results of a normal pearson correlation. It happens that this is not the case for me. What could be the ...
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2answers
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Feature selection for time series data

I am looking for methods for feature selection (or feature extraction) for time series data. Of course I did some research before, but it was not satisfying. I am aware of methods like PCA, ...
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0answers
40 views

Correction of data using a correlation

Suppose I have measured the outcome variable A using a (psychophysical) test that determines the ability of a subject to discriminate between two stimuli with a certain difference (the variable X). It ...
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3answers
707 views

Random variables have non-zero covariance but expected sample covariance is zero? (intuition)

This post asks "why a familiar and widely used estimator of sample covariance has expected value zero, in a situation where the variables involved are characterized by non-zero and equal pair-wise ...
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163 views

Can I use correlation metrics also for time series?

I was using the cross correlation function in R (ccf) until now to discover correlations and lags between two time series. I was wondering if I can use all other ...
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1answer
550 views

Similarity between two samples (2D matrices)

I have two matrices: A= 4000x78 where 78 is the dimension of features and 4000 is the number of samples. B= 1000x78 where 78 is the dimension of features and 1000 is the number of samples again. ...
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1answer
459 views

How to obtain cross-correlation function from cross-spectrum?

I have implemented a piece of code based on the Lomb-Scargle approach for determining the cross-spectrum of two time series. My cross spectrum contains complex numbers and I have used the basic fft ...
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3answers
8k views

Is my time series stationary?

I am using R and have found that both KPSS ( Kwiatkowski-Phillips-Schmidt-Shin ) and the adf (Dickey-Fuller) tests indicate stationarity, having a p-value of 0.01. Here is a plot of the original data:...
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1answer
1k views

How do you generate correlated ARMA(1,1) models?

I am interested in generating two ARMA(1,1) time series with a pre-defined cross-correlation p between x(t) and y(t). If you could please provide the mathematical framework and the code in R for ...
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1answer
178 views

How to Determine whether Simulation Draws are Correct

I have implemented algorithm 1 and 2 in this paper http://www.lse.ac.uk/statistics/documents/researchreport61.pdf for the analysis/simulation hidden states for some time series. The reason why I am ...
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1answer
2k views

How to synchronize two signals using FFT in R?

I have two signals that I want to synchronize. I could achieve this by doing a cross-correlation using the ccf function and finding the lag time at which the ...
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23 views

Cross correlation using photographic film

I used to work for a guy who told me about working for an oil company, probably in the 1960's, doing cross correlation work by sliding two pieces of developed film strips across each other (maybe they ...
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545 views

How to estimate the percent of the variation of a time series explained by another time series (non-stationary)?

I've been learning about time series analysis because I want to understand how much groundwater level changes in an aquifer affect land subsidence (land sinking). I have two time series: (1) ...
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524 views

Linear regression with a delay : $R(t)= a S(t-\delta) + \epsilon$

$R(t)$ corresponds to soil respiration values in function of the time $S(t)$ corresponds to solar radiation values in function of the time $R(t) = a S(t-\delta) + \epsilon$ How calculate the ...
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1answer
964 views

Spatial Cross-correlation Function

I have code that calculates a bias-adjusted estimator xi(r) defined as a measure of the excess probability dP, above what is expected for an unclustered random ...
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2answers
1k views

Reproduce Cross Correlation results in Python

I'm trying and failing to reproduce the results found in this paper, where the cross correlation between two distributions is calculated: ...
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1answer
931 views

Formatting Time-series data for Cross-correlation

In an experiment we measured 100 response times for each subject. The data has the following format: ...
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1answer
3k views

Cross correlation for very sparse binary data

I have a very large (5271159x60) sparse (~2.5%) binary matrix, and I'd like to calculate the cross correlation between each of the columns (sensors) for a series of lags from -10:10, which would give ...
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1answer
70 views

Matching two power signals for similarity

Below are the images of two signals that i plotted. Both the signals are from fridge belonging to different houses. Visually looking at the plot i can tell that these plots belong to fridge as they ...
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1answer
48 views

Maximal coss-correlation formula

I'm reading "Comparing SVM and Convolutional Networks for Epileptic Seizure Prediction from Intracranial EEG" by Yann Lecun et al, and in the paper they present the following formula for maximal ...
3
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1answer
359 views

Counterintuitive result when comparing two groups of time series

I have two groups of time series and I am testing the hypothesis that the groups can be distinguished in some way. Each time series is measurements of an individual’s pupil size as they listen to an ...
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0answers
1k views

Proper normalized cross-correlation

I'm confused with the widely used approach to compute the normalized cross-correlation which is something like this: Standardize the argument vectors (of equal length $n$). Slide one over the other ...
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0answers
69 views

Initiator follower analysis with time series data sets

I am a newbie to this forum. I searched different white papers and codes on google but couldn't find a solution, that's when I registered on this forum.. Please share in case you guys have a idea as ...
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89 views

How to understand this “normalized product-moment correlation” description

I've recently come across this formula from an ITU-T standard in a project that I'm working on. The application of the formula is to compare two vectors containing some per frame statistics from two ...
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0answers
108 views

ANOVA and dependence WITHIN a group

I have three different methods that I would like to compare using ANOVA. The variable to compare is method accuracy that I get trough cross-validation. This means that the same data set (N=60 subjects)...
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1answer
1k views

Cross-correlation in matlab: symmetrical plot and sign convention

I have two cosine signals in MATLAB both having a frequency of 100 Hz and the second signal has been delayed in time by 0.003 seconds. Both signals have been sampled at 1 Khz. When I use the cross ...
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2answers
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Interpreting CCF correlation in R

I am using ccf to find a correlation between 2 time series. I am getting a plot that looks like that: Note that I am mainly interested in correlation for the lag=0....
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1answer
2k views

Cross-correlation in R – dealing with missing values

I have two time series. One is an environmental variable (n = 108) organized by year and month. The other is a biological variable, also organized by year and month, but I have no data for some months ...
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1answer
751 views

Convert Cross Correlation to Probability value

How can I convert the [-1;1] bound cross correlation value to a probability [0;1]. Cross correlation measures the similarity of two signals / images A,B, I aim at expressing this in the probability ...
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4answers
5k views

How to perform proper data mining on time-series data?

I have some daily data from city A, B, C. Values from city A are highly correlated with values from other cities for lag -1,-2,-3 and -4. I want to use Random Forest, SVM and ANN to predict values ...
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1k views

Which Xcorr to choose in a concrete situation: normalized/not, biased/unbiased?

I have 2 data sets, one is binned and another is not, 9000 values each. Something like this: ...
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1answer
773 views

Finding a subset of the data in which two variables are independent

I have a dataset of ~400 subjects. For each subject, I have about 18 variables (V1...V18), all of those continuous and measured at the same timepoint. A paper I'm working on would benefit from ...
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2answers
67 views

Crosscorrelation of stochastic process

Let $Z_1,Z_2 $ i.i.d. standard normal $$ X(t) = \begin{cases} 0, & \text{if } t<Z_1, t<Z_2\\ 1, & \text{if } Z_1\le t <Z_2 \text{ or } Z_2\le t <Z_1 \\ 2, & \text{if } t\ge ...
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64 views

How can I specify cross-correlations between differential equations?

For my Master thesis I want to model co-movements between two commodity forward curve. First, I specify the model for a single forward curve $F(t,T)= \bar{F}_0(t)e^{s(T_i)-y(t,T-t)(T-t)}$ where $F(t,...
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0answers
587 views

Correlation coefficient in longitudinal data

We are performing a longitudinal analysis over different characteristics (variables) of a single subject of analysis. Our goal is not to make any predictions, but rather analyse correlations among ...
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0answers
470 views

Cross-Correlating more than Two Time Series

this is my first post to stackexchange, I have read many solutions, especially to programming questions in R and have appreciated their helpfulness. Currently I find myself stuck with a time series ...
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0answers
337 views

Practical meaning of expected value, standard deviation & correlation

We've got given annual results of two stock companies described with following values: Company X: expected value $\mu_X=0.05$, standard deviation $\sigma_X=0.02$ Company Y: expected value $\mu_Y=0....
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0answers
957 views

Prewhitening time series: ARIMA-modelling versus polynomial trendelimination

I'm concerned with Box-Jenkins-models and especially the first step, the prewhitening to obtain meaningful crosscorrelations for identifying transfer functions and building regression models. I'm ...
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1answer
12k views

Multivariant time series in R. How to find lagged correlation and build model for forecasting

I'm new in the page and pretty new in statistics and R. I'm working on a project for college with the objective of finding the correlation between rain and water flow level in rivers. Once the ...
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339 views

Cross correlation in Stata

I have a cross sectional dataset of investment figures (in $) and a set of dependent variables. The data relates to various years (2000-2013). More than one investment is included in the dataset for ...
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2answers
2k views

Intuition behind auto/cross-correlation

I am really having trouble understanding the intuition behind autocorrelation. I mean why are we even calculating a correlation of some series with itself? Can anybody explain it in lay terms with an ...
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1answer
2k views

Normalized cross correlation vs Euclidean distance in template matching

What is the difference between normalized cross-correlation and Euclidean distance in pattern recognition? -- especially if we want to do recognition with template matching. I understand about ...
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1answer
830 views

Correlating two time series to account for lag and lingering effects

I am trying to find the correlation between two time series, call them A and B. Let's pretend A has the number of successful advertising campaigns for each month for a company, and B has the company's ...
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2answers
2k views

Statistical comparison of two signals

I need to develop an algorithm that will compare two signals and generate some metric(s) to describe changes between them. Signal processing and analysis isn’t my strong point so I would appreciate ...
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1answer
4k views

Cross-correlation in Matlab

What is the difference between: 1) xcov(x,y,10,'unbiased')/sqrt(xcov(x,x,0,'unbiased')*xcov(y,y,0,'unbiased')); 2) xcorr(x,y,10,'unbiased'); 3) [A, B] = crosscorr(x,y,10); ? I think (but I am not ...
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276 views

Estimating the dof for t test of Correlation Coefficients of smoothed time courses

I'm working with an array of size 265 x 5000. Each column is a time series and the rows are points in a series of volumes ( voxels in fMRI ). I preprocessed this data in several ways, most of which ...
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Correlation between two variables over time

I have 5 individuals. I measure variable X and Y of each one of them over time (on 5 different time points). I want to find out if there are any correlations between X and Y over time and show the ...
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1answer
3k views

Comparing time series: Pearson correlation, Kendall's tau b or Spearman's rho?

Which correlation coefficient is the most appropriate to compare 2 time series? I want to compare the variation of one variable for 2 regions, have regional data for the last 30 years. Is Pearson ...