All Questions
Tagged with variogram autocorrelation
17 questions
6
votes
1
answer
102
views
Checking for temporal autocorrelation in experience sampling data - how to interpret the variogram?
I have day-level data from about 100 participants from 11 days (EDIT. a subset of participants responded for 12 days, which is why there's a distance of 11 in the variogram table). I'm interested in ...
- 2,815
0
votes
0
answers
32
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Creating a Variogram-like plot with distances
I have a dataset of points in space, sampled at a specified time. Now i want to obtain a 'spatial correlation plot, only between points close in time'.
What i did is creating a dataframe of pairs of ...
- 9
0
votes
0
answers
212
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Variogram of categorial data?
I have a thematic map as raster data with classes assigned as numbers: 1,2,3,4. These are categorial classes and have no linear meaning. I am interested if there is spatial autocorrelation in this ...
- 133
2
votes
0
answers
35
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I am not sure if my data are spatially autocorrelated or not.
I have been trying to figure out if my data are spatially autocorrelated by generating semivariogram of the residuals. I do not get the shape similar to any variogram (spherical, exponential or ...
- 51
0
votes
0
answers
326
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Why is my semivariance so high?
I am using variograms checking for spatial autocorrelation in a resiudal pattern produced by a GLMM-NB. In theory, the semivariance should be bounded between 0 and 1 (that´s what I think at least as I ...
- 1,635
2
votes
1
answer
530
views
What does it mean that a variogram keeps increasing with distance?
I am modeling my 3D dataset with a Gaussian Process with square-exponential covariance. To test whether this is a good model, I subtract the mean from the observed data and then calculate the ...
- 1,002
0
votes
0
answers
264
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Variogram with custom distance matrix
I work in marine ecology and as such all of my distance matrices are constructed using the shortest possible marine route - i.e. avoiding any land. Here is a plot of my "marine distances" against "as ...
- 1
1
vote
0
answers
395
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Deriving the ordinary kriging equations with noisy data
I am trying to derive the ordinary kriging equations when I want to estimate the underlying value at $T(x_0)$ from the noisy observations at its neighbors $Z(x_1),....Z(x_n)$.
$Z(x_0) = T(x_0) + \...
- 6,847
8
votes
1
answer
663
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Issues with ordinary kriging
I was following this wiki article related to ordinary kriging
Now my covariance matrix looks like this, for 4 variables
...
- 6,847
2
votes
1
answer
155
views
How to recover the underlying observations from the noisy ones using gaussian processes
I have some simulated experiments where I generate some samples with an exponential correlation function. I am assuming a spatial grid whose variables form a multivariate gaussian distribution with an ...
- 6,847
3
votes
1
answer
280
views
Confusion related to estimation of nugget
I am generating some simulated data from a multivariate gaussian distribution with a covariance matrix sigma. To add some noise, I added an identity matrix to the covariance matrix which depicts ...
- 6,847
2
votes
0
answers
364
views
Estimating the autocorrelation function with some noisy observations
I am wondering how to estimate the actual correlation function when I have some noisy samples of some space. Lets say, I have a space and the locations in the space are variables following a ...
- 1,521
2
votes
0
answers
240
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how to generate samples with the given autocorrelation function [duplicate]
I want to generate some spatial data where the points/location in the space form a multivariate gaussian distribution. I want these points to have certain autocorrelation given by the variogram model ...
- 6,847
3
votes
0
answers
334
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Issues with fitting a variogram
I am trying to fit a spherical variogram to some synthetic data using the code available at http://www.mathworks.com/matlabcentral/fileexchange/25948-variogramfit. However, I have some doubts. I ...
- 6,847
1
vote
1
answer
460
views
Fitting a correlation function to my data
I have some spatial data and I want to fit a correlation function may be exponential or gaussian to my data. I could calculate the correlation for different pairs of my spatial point to get some ...
- 6,847
3
votes
0
answers
599
views
Calculating R-squared values from a semivariogram
I have some spatially autocorrelated vegetation data, and would like to know the how well tree size measured at one location can predict tree size in plots 100m away.
I've made a semivariogram of ...
- 1,215
5
votes
1
answer
2k
views
Is there an intuitive interpretation of a negative variogram "nugget" value?
A variogram plots the variance of the difference between sample pairs on a field (any dimensionality) against spatial separation (the "lag") of those samples.
The extrapolation from observed small-...
- 151