A function to draw a sample from the posterior of a spatial LGCP. Randomly selects an index i, and returns the ith value of eta, the ith value of beta and the ith value of Y as a named list.
samplePosterior(x)
an object of class lgcpPredictSpatialOnlyPlusParameters or lgcpPredictAggregateSpatialPlusParameters
a sample from the posterior named list object with names elements "eta", "beta" and "Y".