Description Usage Arguments Value Note Author(s) References See Also

Fit a Linear Model of Coregionalization to a Multivariable Sample Variogram; in case of a single variogram model (i.e., no nugget) this is equivalent to Intrinsic Correlation

1 2 |

`v` |
multivariable sample variogram, output of variogram |

`g` |
gstat object, output of gstat |

`model` |
variogram model, output of vgm; if supplied this value is used as initial value for each fit |

`fit.ranges` |
logical; determines whether the range coefficients (excluding that of the nugget component) should be fitted; or logical vector: determines for each range parameter of the variogram model whether it should be fitted or fixed. |

`fit.lmc` |
logical; if TRUE, each coefficient matrices of partial sills is guaranteed to be positive definite |

`correct.diagonal` |
multiplicative correction factor to be applied to partial sills of direct variograms only; the default value, 1.0, does not correct. If you encounter problems with singular covariance matrices during cokriging or cosimulation, you may want to try to increase this to e.g. 1.01 |

`...` |
parameters that get passed to fit.variogram |

returns an object of class `gstat`

, with fitted variograms;

This function does not use the iterative procedure proposed by M. Goulard and M. Voltz (Math. Geol., 24(3): 269-286; reproduced in Goovaerts' 1997 book) but uses simply two steps: first, each variogram model is fitted to a direct or cross variogram; next each of the partial sill coefficient matrices is approached by its in least squares sense closest positive definite matrices (by setting any negative eigenvalues to zero).

The argument `correct.diagonal`

was introduced by experience: by
zeroing the negative eigenvalues for fitting positive definite partial
sill matrices, apparently still perfect correlation may result, leading
to singular cokriging/cosimulation matrices. If someone knows of a more
elegant way to get around this, please let me know.

Edzer Pebesma

variogram, vgm, fit.variogram,
`demo(cokriging)`

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