# 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.

70 questions
Filter by
Sorted by
Tagged with
1answer
34 views

### How do you express the variogram $\gamma(u)$ in terms of correlation for a stationary process?

The Analysis of Longitudinal Data textbook by Diggle et al. (2002) mentioned twice (p48 f. and then on p82) that given the following definition of the variogram, \begin{equation} \gamma(u) = \frac{1}...
0answers
15 views

### How to generate two spatial data sets with different levels (low and high) of spatial autocorrelation?

Spatially correlated random fields can be generated (for example using geoR or gstat packages in R) by defining a model for the semi-variogram (e.g. exponential, gaussian, spherical, etc), as well as ...
0answers
24 views

### No convergence when fitting theoretical semivariogram to empirical?

I'm kind of new to working with semivariograms. But I just wanted to fit a semivariogramm to my data and when fitting the theoretical variogram to my empirical it tells me that: ...
0answers
27 views

### Interpreting a Distance & Time 3D Variogram for Variogram modeling

I am trying to understand some concepts of variograms. I have made several variogram models in R and am trying to understand exactly what they mean. My data is ...
0answers
39 views

### Variogram fit in R not converging

I have taken a shapefile from Open NYC Data and performed the following method. My end goal is to predict Taxi trip_duration at various points across the city of ...
0answers
25 views

### 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 ...
0answers
26 views

### Why do you need a variogram for Kriging? goldingn/gpe package?

I am using golingn/gpe (github) package, and it does not provide a variogram and instead look at co-variances. Is it possible to do kriging without providing variograms?
0answers
10 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 ...
0answers
28 views

### Should a nugget ever shift the variogram away from zero at distance zero?

I had frequently seen the definition for a "rigorous" spatial isotropic semivariogram being defined as: $$\gamma(h) = K(0) - K(h)$$ Where $K$ is a positive definite covariance matrix. If the ...
0answers
422 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 ...
0answers
61 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 ...
0answers
102 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 ...
1answer
196 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 ...
0answers
142 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 ...
2answers
7k 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 ...
2answers
608 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 ...
1answer
156 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 ...
0answers
487 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. ...
1answer
215 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 ...
0answers
84 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 ...
0answers
380 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 ...
0answers
32 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 ...
0answers
268 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 ...
1answer
459 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 ...
0answers
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 ...
0answers
26 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 ...
0answers
123 views

0answers
143 views

### Non-parametric variogram estimators

I'm working with overdispersed, count spatial data. The goal is to look specifically at spatial dependence patterns. I'm trying to fit variogram models to empirical variograms, however the only ...
1answer
340 views

### Lag lengths are larger than my domain in gstat in R? variogram object

My problem is that the my resulting variograms are of a larger lag length than my domain. I have the following code to compute lags in the vertical direction: ...
1answer
798 views

### Fitting a variogram model with the pairwise distance matrix supplied

I'm trying to fit a variogram to my data, however the spatial points are confined by an irregular polygon. So I'd like to supply a variogram model function with the distance matrix of the points. I'...
0answers
55 views

### Measurament error from semivariogram

I am looking at a model to determine the measurement error for a set of measurements of a spatially correlated phenomenon (sea surface temperature measurements) using a semivariogram technique. For ...
0answers
427 views

### Universal kriging: which variogram to use?

I am working with the build in dataset meuse, which has 155 measurements of Zinc and the distance to the river "Meuse".(http://rspatial.r-forge.r-project.org/gallery/). Now I am trying to imitate ...
1answer
302 views

### Kriging results are too localized, how can I increase the influence of each data point

I have a small dataset that looks like this... ...
0answers
193 views

### AIC or similar selection techniques for Variograms?

I have a very basic question: how does one choose the "best" variogram? It is possible to fit different models to an empirical variogram, e.g. nugget, ...
1answer
841 views

### R Error in chol.default(A) krigeST from gstat package

I am working with an hourly dataset of air temperature, recorded at ~200 stations over a relatively small area. I chose a space-time variogram (e.g. sum-metric) to fit my data and am now trying to ...
1answer
295 views

### Weights in the fit.variogram method of gstat

I'd like to know if I understood correctly the following. In the fit.variogram method of the gstat library, there is a fit.method...
2answers
327 views

### What effect does data averaging have on the variogram?

What effect does data averaging have on the variogram? To be specific, please see a simple example: ...
0answers
122 views

### Variance and Variograms: Sigma?

Can someone please walk me through this morass of σ's? There is a sigmasq in the summary output from geoR's likfit. Really this is the one I'd like to know about. I'm not clear which of all of the ...
0answers
116 views

### Details on kriging and variograms

I was wondering what are the steps to perform factoring kriging. I know it is used to extract specific components that may have a physical meaning and this is achieved by kriging. However, I have some ...
0answers
310 views

### Strange results in kriging with geoR. Is this a bug? Am I doing something silly? Or is this data set just unfortunate?

I am performing kriging on a large number of relatively modest data sets (144 data points on a 9 x 16 grid in each data set). I was experimenting with different variogram models and other parameter ...