'How to set positive the range of my variogram fit for krige?

I want to interpolate with krige samples of pollution, but when I was fitting my variogram, the range resulted negative, and it must to be positive. I runned this:

head(muestras)
  Index SAMPLE ZONE EASTING NORTHING  Latitude Longitude        Mg      Bal       Al
1     1   Al01  19K  535234  7528392 -22.35000 -68.65781 20155.623 523711.3 14897.99
2     2   Al02  19K  538091  7533652 -22.30242 -68.63019 18240.623 527488.0 30534.27
3     3   Al03  19K  540850  7549211 -22.16180 -68.60380 12797.157 533882.2 45389.78
4     4   Al04  19K  543208  7561915 -22.04697 -68.58127  7748.070 539969.0 60457.23
5     5   Al05  19K  552494  7579475 -21.88807 -68.49184  6646.537 542206.5 61427.67
6     6   Al06  19K  553310  7571159 -21.96318 -68.48367  6764.483 545600.1 62231.17

coordinates(muestras) <- ~ Latitude + Longitude

#Model
mod <- lm(Ca ~ Latitude + Longitude, as.data.frame(muestras))

#Variogram
variog_mod <- variogram(Ca ~ 1, data = muestras)
plot(variog_mod)

fit.vgm <- fit.variogram(variog_mod, vgm("Sph", nugget = 1060365658,
                                   psill = 151716381,
                                   range = -1.776595))

After trying to run fit.variogram(), R throw the following error:

Error in vgm("Sph", nugget = 1060365658, psill = 151716381, range = -1.776595) : 
  range should be positive

Could you help me to set positive the range? I would appreciate it.

Regards.

Sources

This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.

Source: Stack Overflow

Solution	Source

'How to set positive the range of my variogram fit for krige?

Sources

Related Questions