lecture 1: introduction to spatial point processes · 1.longleaf dataset (r package spatstat)....

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Spatial datasets Definition and theoretical characterization Moment measures and intensity functions Lecture 1: Introduction to spatial point processes Jean-Fran¸ cois Coeurjolly http://www-ljk.imag.fr/membres/Jean-Francois.Coeurjolly/ 1 / 19

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  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Lecture 1: Introduction to spatial pointprocesses

    Jean-François Coeurjollyhttp://www-ljk.imag.fr/membres/Jean-Francois.Coeurjolly/

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  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Description of the course

    • This introduction is divided into 4 lectures :1. Introduction : examples, general definitions.2. Poisson point process.3. Summary statistics.4. Models for spatial point processes.

    • Material : slides, datasets, R instructions used for thelectures can be found athttp://www-ljk.imag.fr/membres/Jean-

    Francois.Coeurjolly/

    • You are asked to prepare some of the theoretical exercisesand practical exercises (using the R software) at home.

    • You are also asked to read a research paper (to be givennext week) and prepare a one-page summary of the paper(either in French or English).

    2 / 19

  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Special thanks to . . .

    the Danish team : Jesper Mølle, Ege Rubak and RasmusWaagepetersen

    and Adrian Baddeley (Australia), Rémy Drouilhet (Grenoble) andYongtao Guan (USA)

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  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Examples of spatial point pattern data

    General definitions and characterization

    Moment measures and intensity functions

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    Spatial data . . .

    . . . can be roughly and mainly classified into three categories :

    1. Geostatistical data : modelling of a discrete/continuous(vector) real-valued random variable observed at fixedlocations of a continuous space.

    2. Lattice data : modelling of a discrete/continuous (vector)real-valued random variable observed at fixed locations of adiscrete space.

    3. Spatial point pattern : modelling of random locations ofpoints (or objects) observed on a continuous space.

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  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Geostatistical data• sic.100 dataset (R package geoR) : cumulative rainfall in

    Switzerland the 8th May.

    • The observation consists in a discretized sample path of arandom field, X = (Xu , u ∈ R2),Xu ∈ R.

    • Scientific questions : spatial correlation modelling (covariance,variogram), trend and variogram estimation, spatial prediction =kriging.

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  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Lattice data

    • Lightning density =number of lightning strikesper square kilometer peryear in 2013.

    • The data are aggregated bydepartment ⇒ randomfield on a network,X = (Xu , u ∈ G),Xu ∈ Rwhere G is a graph.

    • Scientific questions : spatial neighborhood correlation, spatialhomogeneity or inhomogeneity, discrete spatial modelling,. . .

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  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Spatial point pattern : forestry datasets• Observation of 65, 71 and 126 japanese, swedish and finnish pines

    on W = [5.7, 5.7]2, [−5, 5] × [−8, 2] and [0, 9.6] × [0, 10] (in m).• The locations and the number of points are random !• The state space is denoted by S = R2 and is equipped with ‖ · ‖.

    japanese pines

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    Scientific questions :

    • Understanding of the arrangement of the points : is thearrangement spatially homogeneous or inhomogeneous.

    • Are the points independent one from each other (CSR) or dothey exhibit a particular structure (clustered or repulsion) ?

    • Among the three species, which one has the highest intensity ? Isthis difference significant ? 8 / 19

  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Spatial point pattern : earth quakes dataset

    • R package dataset.• The data set give the locations of 1000 seismic events of

    MB > 4.0. The events occurred in a cube near Fiji since 1964.

    Scientific questions :

    • Can we estimate the spatialinhomogeneity of seismicevents ?

    • Can we prove statistically thepresence of two main clusters ?

    • Can we highlight theanisotropy ?

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  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Spatial point pattern : earth quakes dataset

    • R package dataset.• The data set give the locations of 1000 seismic events of

    MB > 4.0. The events occurred in a cube near Fiji since 1964.

    Scientific questions :

    • Can we estimate the spatialinhomogeneity of seismicevents ?

    • Can we prove statistically thepresence of two main clusters ?

    • Can we highlight theanisotropy ?

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  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Spatial point pattern : marked point process1. Longleaf dataset (R package spatstat). Locations of 584 trees

    observed with their diameter at breast height. S = R2 × R+(equipped with max(‖ · ‖, | · |)).

    2. Ants dataset (R package spatstat). Locations of 97 antscategorised into two species. S = R2 × {0, 1} (equipped with themetric max(‖ · ‖, dM ) for any distance dM on the mark space).

    longleaf

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    Scientific questions :

    1. Are large trees independent ? Do large trees influence thepositions of smaller ones ?

    2. Is there any competition inside each specie ? Are the two speciesindependent ?

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  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Spatial point pattern with extra information

    • chorley dataset (R packagespatstat)

    • Cases of larynx and lungcancers and position of anindustrial incinerator.

    • S = R2 × {0, 1} (equipped withthe metric max(‖ · ‖, dM ) forany distance dM on the markspace).

    Chorley−Ribble Data

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    Scientific questions :

    • Can we input the spatial positions of cancer cases to thepresence of the industriel incinerator ? to any other extrainformation (population density,. . .) ?

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  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Spatial point pattern with spatial covariates• Beischmedia dataset (R package spatstat, large tropical forest

    dataset).

    • 3604 locations of trees observed with two spatial covariates (herethe elevation field, gradient of the elevation).

    Scientific questions :

    • Can we explain the spatialinhomogeneity by the elevation,the slope ?

    • Can we statistically prove thepositive influence of these twocovariates ?

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  • Spatial datasets Definition and theoretical characterization Moment measures and intensity functions

    Spatio-temporal point process• Lightning strikes observed on the domain [−5, 9] × [42, 53]

    (long,lat) observed temporally since the period 2010-2013.

    • Both time and position are point processes ; S = R2 × R. Summer 2010

    5000

    1000

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