Questions tagged [variogram]

A plot or function used in spatial statistics (or in time series analysis) to describe the degree of spatial (or time) dependence of a stochastic process.

61 questions
8 views

why variogram models take only one independent variable

lznr.vgm = variogram(log(zinc)~sqrt(dist), meuse) i am using meuse data for practicing to create variogram models, but i am confused to know there are 14 ...
29 views

How do nugget interactions work in Gaussian Processes/Kriging?

How do nuggets and nugget interactions fit into the variogram framework? I am especially interested in the case where there is more than one distance term being used (e.g. space and time): where you ...
198 views

Problems fitting a model to a variogram

I am having problems fitting a variogram model. I tried to change some parameters to estimate or fix them but I am still not achieving any improvement. I remove trend of the data and use logarithms ...
33 views

Cokriging, zero distance semivariance [gstat]

Trying cokriging with simulated data, I faced a problem that did not seem one in the demo(cokriging) with the meuse dataset: I can't use ...
51 views

How to interpret semivariogram parameters from two different raster images?

I know the definitions of the components of a semivariogram. However, I would want to know how they could be interpreted when applied to actual scenarios. For instance, I have two EVI (enhanced ...
69 views

How can I understand these variograms?

Using grf function from R package geoR, I simulated 6 replicates (each with 1000 samples) of a Gaussian random field on ...
77 views

Mixed model with serial correlation and random slope?

I'm making a mixed model for some longitudinal data, where the response is measured fro multiple individuals over time. I have made a model with random intercept, random slope and gaussian serial ...
4k views

What is the nugget effect?

I don't understand exactly what is meant by the term "nugget effect" in geostatistics. When looking at empirical variograms plotting the variogram $\gamma(h)$ vs. the lag $h$, the nugget is defined as ...
324 views

Temporal Variogram

Can we compute temporal variograms just like spatial variograms? I know about spatio-temporal variograms but I am more interested in doing a comparison of separate spatial and temporal variograms and ...
109 views

How do you interpret this variogram?

Description: 8000 spatial data points spanned over an entire state 200 bins are used My question: Is the variogram telling something about the nature of the data? Why is it fluctuating? Should I do ...
353 views

Spherical vs. Exponential Kriging Covariance Functions

A statistical epidemiologist colleague of mine told me that in comparing spherical vs exponential kriging covariance functions, only the latter (i.e., exponential) function is generally a valid model. ...
160 views

How SHOULD a variogram plot look like?

Say you fit a model m. You then calculate the variogram. In R, this can e.g. be done by using plot.Variogram using the nlme package on an lme object. Say the plot indicates that yes, there is some ...
67 views

Explain Like I'm Five version for Variograms in R's gstat package

Long story short, I asked a question on StackOverflow about Variograms in the gstat package in R. The person who answered gave me some tips on creating the variogram using the package. My dataset is ...
273 views

warning when fitting variogram - gstat

I'm trying to build a variogram model of the semi variance in Zn concentration with distance using gstat package in R. First I plot the variogram based on my data (it clearly seems to mean that the ...
28 views

Variogram to constrain kernel density bandwidth

I have linear structures transformed into points and spatially distributed like this: I want to perform a kernel density so that zones with lots of structures present high density. The problem is ...
226 views

How much difference in the Akaike Information Criterion is reasonable between a Spatial and a Non spatial Model

I am doing supervised land value modelling (900 observations) and I am comparing two approaches to do a variable selection (51 variables). I am using R. The first one is a backward step-wise ...
319 views

Why is positive definiteness necessary for kriging?

I understand from wikipedia that a variogram model must be positive definite to be used for kriging: Note that the experimental variogram is an empirical ...
30 views

Is there a way to find optimal sensor node locations in a domain when all data is known?

I have an x-y domain where I know the snow depth everywhere. (i.e. the granularity of the values is such that I can assume I know it everywhere). I want to use this information to inform where to ...
25 views

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 ...
112 views

455 views

Issues with ordinary kriging

I was following this wiki article related to ordinary kriging Now my covariance matrix looks like this, for 4 variables ...
147 views

Matrix singularity issues with gaussian variogram [closed]

I have defined my gaussian variogram like this $r(h) = \text{nugget} + \text{partial_sill}\cdot(1 - \exp(-\frac{3h^2}{\text{range}^2}))$ I set nugget = 0.1343 partial_sill = 0.3125 range = 19.8642 ...
90 views

Confusion related to ordinary kriging

I was reading this wiki article related to ordinary kriging where they calculated the weights like this I know that covariance from the covariogram and semivariance from the semivariogram are ...
103 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 ...