# ffbs.spectral: Forward Filtering Backward Sampling algorithm in the spectral... In spate: Spatio-Temporal Modeling of Large Data Using a Spectral SPDE Approach

## Description

Forward Filtering Backward Sampling algorithm for sampling from the joint full conditional of the coefficients α and for evaluation of the log-likelihood.

## Usage

 1 2 ffbs.spectral(w=NULL,wFT=NULL,spec=NULL,Gvec=NULL,tau2=NULL,par=NULL,n,T,lglk=FALSE, BwSp=TRUE,NF=n*n,indCos=(1:((n*n-4)/2)*2+3),ns=4,nu=1,dt=1) 

## Arguments

 w Observed data or latent process w (depending on which data model is used) in an T x n*n matrix with columns and rows (points on a grid stacked into a vector) corresponding to time and space, respectively. wFT Vector of length T*n*n containing the real Fourier transform of 'w'. spec Spectrum of the innovations \hat{ε} in a vector of length n*n. If 'spec' is not given, it is constructed based on 'par'. Gvec The propagator matrix G in vector format obtained from 'get.G.vec'. If 'Gvec' is not given, it is constructed based on 'par'. tau2 Measurement error variance tau2. If 'NULL'; tau2=par[9]. par Vector of parameters for the SPDE in the following order: rho_0, sigma^2, zeta, rho_1, gamma, alpha, mu_x, mu_y, tau^2. If 'spec' and 'Gvec' are given, 'par' will not be used. n Number of grid points on each axis. n*n is the total number of spatial points. T Number of points in time. lglk Logical; if 'TRUE' the value of the log-likelihood is returned as well. BwSp Logical; if 'TRUE' a sample from the full conditional of α is returned. NF Number of Fourier functions used. indCos Vector of integers indicating the position cosine terms in the 1:NF real Fourier functions. The first 'ns' cosine wavenumbers in 'wave' are not included in 'indCos'. ns Number of real Fourier functions that have only a cosine and no sine term. 'ns' is maximal 4. nu Smoothness parameter of the Matern covariance function for the innovations. By default this equals 1 corresponding to the Whittle covariance function. dt Temporal lag between two time points. By default, this equals 1.

## Value

A list with entries (depending on whether 'lglk' are 'BwSp' are 'TRUE' or 'FALSE'):

 simAlpha A T x n*n matrix with a sample from the full conditional of latent process α, ll The evaluated log-likelihood,

## Author(s)

Fabio Sigrist

spate documentation built on May 29, 2017, 11:37 a.m.