[R-sig-Geo] Practical range spatial dependency- Exponential variogram model

[Edzer Pebesma]

On 03/27/2014 03:04 AM, Moshood Agba Bakare wrote:
> Dear All,
> 
> An exponential model is fitted to empirical semivariogram using *gstat of R
> package*. The variogram parameters obtained is
>   model      psill   range
> 1   Nug 0.04281109 0.00000
> 2   Exp 0.76810071 5.45954
> where the nugget effect is 0.04, sill is approximately 0.80, and range is
> 5.5.
> Since exponential model approaches the sill asymptotically, its practical
> range of spatial dependency is reported by literature to be distance at
> which the semivariance is 95% of the sill.
> Having obtained 5.5 as my range from the analysis, how do I estimate the
> practical range at 95% of sill?

3 * range:

> 1-exp(-3)
[1] 0.9502129

which can be confirmed by:

> variogramLine(vgm(1, "Exp", 1), dist_vector = 3)
  dist     gamma
1    3 0.9502129

> 
> Thank you.
> 
> 	[[alternative HTML version deleted]]
> 
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-- 
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Heisenbergstraße 2, 48149 Münster, Germany. Phone: +49 251
83 33081 http://ifgi.uni-muenster.de GPG key ID 0xAC227795

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