34 research outputs found
Functional summary statistics for point processes on the sphere with an application to determinantal point processes
We study point processes on , the -dimensional unit sphere
, considering both the isotropic and the anisotropic case, and
focusing mostly on the spherical case . The first part studies reduced
Palm distributions and functional summary statistics, including nearest
neighbour functions, empty space functions, and Ripley's and inhomogeneous
-functions. The second part partly discusses the appealing properties of
determinantal point process (DPP) models on the sphere and partly considers the
application of functional summary statistics to DPPs. In fact DPPs exhibit
repulsiveness, but we also use them together with certain dependent thinnings
when constructing point process models on the sphere with aggregation on the
large scale and regularity on the small scale. We conclude with a discussion on
future work on statistics for spatial point processes on the sphere
Score, Pseudo-Score and Residual Diagnostics for Spatial Point Process Models
We develop new tools for formal inference and informal model validation in
the analysis of spatial point pattern data. The score test is generalized to a
"pseudo-score" test derived from Besag's pseudo-likelihood, and to a class of
diagnostics based on point process residuals. The results lend theoretical
support to the established practice of using functional summary statistics,
such as Ripley's -function, when testing for complete spatial randomness;
and they provide new tools such as the compensator of the -function for
testing other fitted models. The results also support localization methods such
as the scan statistic and smoothed residual plots. Software for computing the
diagnostics is provided.Comment: Published in at http://dx.doi.org/10.1214/11-STS367 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
On simulation of continuous determinantal point processes
We review how to simulate continuous determinantal point processes (DPPs) and
improve the current simulation algorithms in several important special cases as
well as detail how certain types of conditional simulation can be carried out.
Importantly we show how to speed up the simulation of the widely used Fourier
based projection DPPs, which arise as approximations of more general DPPs. The
algorithms are implemented and published as open source software
Determinantal point process models on the sphere
We consider determinantal point processes on the -dimensional unit sphere
. These are finite point processes exhibiting repulsiveness and
with moment properties determined by a certain determinant whose entries are
specified by a so-called kernel which we assume is a complex covariance
function defined on . We review the appealing
properties of such processes, including their specific moment properties,
density expressions and simulation procedures. Particularly, we characterize
and construct isotropic DPPs models on , where it becomes
essential to specify the eigenvalues and eigenfunctions in a spectral
representation for the kernel, and we figure out how repulsive isotropic DPPs
can be. Moreover, we discuss the shortcomings of adapting existing models for
isotropic covariance functions and consider strategies for developing new
models, including a useful spectral approach
Leverage and influence diagnostics for Gibbs spatial point processes
For point process models fitted to spatial point pattern data, we describe diagnostic quantities analogous to the classical regression diagnostics of leverage and influence. We develop a simple and accessible approach to these diagnostics, and use it to extend previous results for Poisson point process models to the vastly larger class of Gibbs point processes. Explicit expressions, and efficient calculation formulae, are obtained for models fitted by maximum pseudolikelihood, maximum logistic composite likelihood, and regularised composite likelihoods. For practical applications we introduce new graphical tools, and a new diagnostic analogous to the effect measure DFFIT in regression