Description Usage Arguments Details Value Author(s) Examples

Spectrum of the Matern covariance function. Note that the spectrum is
renormalized, by dividing with the sum over all frequencies so that
they sum to one, so that
*σ^2* is the marginal variance no matter how many
wavenumbers are included.

1 | ```
matern.spec(wave, n, ns=4, rho0, sigma2, nu = 1, norm = TRUE)
``` |

`wave` |
Spatial wavenumbers. |

`n` |
Number of grid points on each axis. n x n is the total number of spatial points. |

`ns` |
Integer indicating the number of cosine-only terms. Maximally this is 4. |

`rho0` |
Range parameter. |

`sigma2` |
Marginal variance parameter. |

`nu` |
Smoothness parameter of the Matern covariance function. By default this equals 1 corresponding to the Whittle covariance function. |

`norm` |
logical; if 'TRUE' the spectrum is multiplied by n*n so that after applying the real Fourier transform 'real.FFT' one has the correct normalization. |

The Matern covariance function is of the form

*σ^2 2^(1-ν) Γ(ν)^{-1} (d/ρ_0)^{ν} K_{ν}(d/ρ_0)*

with 'd' being the Euclidean distance between two points and K_nu(.) a modified Bessel function. Its spectrum is given by

*2^{ν-1} ν ((1/ρ_0)^(2ν)) (π*((1/ρ_0)^2 + w)^(ν + 1))^{-1}*

where 'w' is a spatial wavenumber.

Vector with the spectrum of the Matern covariance function.

Fabio Sigrist

1 2 3 4 5 |

```
Loading required package: mvtnorm
Loading required package: truncnorm
```

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