Bias Correction for Fitted Model
Applies a first-order bias correction to a fitted model.
bc(fit, ...) ## S3 method for class 'ppm' bc(fit, ..., nfine = 256)
fit |
A fitted point process model (object of class |
... |
Additional arguments are currently ignored. |
nfine |
Grid dimensions for fine grid of locations. An integer, or a pair of integers. See Details. |
This command applies the first order Newton-Raphson bias correction method of
Baddeley and Turner (2014, sec 4.2) to a fitted model.
The function bc is generic, with a method for fitted point
process models of class "ppm".
A fine grid of locations, of dimensions nfine * nfine or
nfine[2] * nfine[1], is created over the original window of the
data, and the intensity or conditional intensity of the fitted model is
calculated on this grid. The result is used to update the fitted
model parameters once by a Newton-Raphson update.
This is only useful if the quadrature points used to fit the original
model fit are coarser than the grid of points specified by
nfine.
A numeric vector, of the same length as coef(fit), giving updated
values for the fitted model coefficients.
Adrian Baddeley Adrian.Baddeley@curtin.edu.au and Rolf Turner r.turner@auckland.ac.nz.
Baddeley, A. and Turner, R. (2014) Bias correction for parameter estimates of spatial point process models. Journal of Statistical Computation and Simulation 84, 1621–1643. DOI: 10.1080/00949655.2012.755976
fit <- ppm(cells ~ x, Strauss(0.07))
coef(fit)
if(!interactive()) {
bc(fit, nfine=64)
} else {
bc(fit)
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