Definitions
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun statistics A
function of the spatial dependence ofvariance ; agraph of this function
Etymologies
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Examples
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The variogram is the key function in geostatistics as it will be used to fit a model of the spatial/temporal correlation of the observed phenomenon.
More ISO-2000 Weather Stations from Jones and Hansen « Climate Audit 2007
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Before I had this thing running, the measure of autocorrelation I was using in my accent model was to crank out a semivariogram for all the point pairs, add up the average value-distance for all the pairs on the “near” half of the variogram, add up the average for the “far” half, and compare the ratio of the “near” and “far” averages.
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A plot of the semivariance versus h is the variogram.
More ISO-2000 Weather Stations from Jones and Hansen « Climate Audit 2007
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When a variogram is used to describe the correlation of different variables it is called cross-variogram.
More ISO-2000 Weather Stations from Jones and Hansen « Climate Audit 2007
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One is thus making a distinction between the experimental variogram that is a visualisation of a possible spatial/temporal correlation and the variogram model that is further used to define the weights of the kriging function.
More ISO-2000 Weather Stations from Jones and Hansen « Climate Audit 2007
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Note that the experimental variogram is an empirical estimate of the covariance of a Gaussian process.
More ISO-2000 Weather Stations from Jones and Hansen « Climate Audit 2007
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For observations at locations the empirical variogram is defined as Cressie 1993:
More ISO-2000 Weather Stations from Jones and Hansen « Climate Audit 2007
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The sampling variogram, unlike the semivariogram and the variogram, shows where a significant degree of spatial dependence in the sample space or sampling unit dissipates into randomness when the variance terms of a temporally or in-situ ordered set are plotted against the variance of the set and the lower limits of its 99% and 95% confidence ranges.
More ISO-2000 Weather Stations from Jones and Hansen « Climate Audit 2007
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By contrast the variogram is well defined for the much wider class of so-called intrinsic processes, its classical estimator is unbiased when the process is only mean stationary and an alternative but natural estimator has only a small bias even when the process is neither mean nor variance stationary.
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This explains why only a limited number of variogram models are used like the linear, the spherical, the gaussian and the exponential models, to name only those that are the most frequently used.
More ISO-2000 Weather Stations from Jones and Hansen « Climate Audit 2007
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