spatstat {spatstat} | R Documentation |
This is a summary of the features of
spatstat
, a package in R
for the statistical analysis of spatial point patterns.
spatstat
is a package for the statistical analysis
of spatial data. Currently, it deals mainly with the analysis of
patterns of points in the plane. The points may carry `marks',
and the spatial region in which the points were recorded
may have arbitrary shape.
The package supports
The point process models to be fitted
may be quite general Gibbs/Markov models; they may include spatial trend,
dependence on covariates, and interpoint interactions of any order (i.e.
not restricted to pairwise interactions). Models are specified by
a formula
in the R
language, and are fitted using
a single function ppm
analogous to
lm
and glm
.
Type demo(spatstat)
for an overall demonstration
of the package.
An introduction to the package is available in the
file Intro.pdf
in the doc
directory supplied in the
installation of the package.
The package is described more fully in the paper by Baddeley and Turner (2005a), available online.
Following is a summary of the main functions and datasets
in the spatstat
package.
Alternatively an alphabetical list of all functions and
datasets is available by typing library(help=spatstat)
.
For further information on any of these,
type help(name)
where name
is the name of the function
or dataset.
To create a point pattern:
ppp | create a point pattern from (x,y) and window information |
ppp(x, y, xlim, ylim) for rectangular window |
|
ppp(x, y, poly) for polygonal window |
|
ppp(x, y, mask) for binary image window |
|
as.ppp | convert other types of data to a ppp object |
setmarks , %mark% | attach/reassign marks to a point pattern |
To simulate a random point pattern:
runifpoint | generate n independent uniform random points |
rpoint | generate n independent random points |
rmpoint | generate n independent multitype random points |
rpoispp | simulate the (in)homogeneous Poisson point process |
rmpoispp | simulate the (in)homogeneous multitype Poisson point process |
rMaternI | simulate the Mat'ern Model I inhibition process |
rMaternII | simulate the Mat'ern Model II inhibition process |
rSSI | simulate Simple Sequential Inhibition process |
rNeymanScott | simulate a general Neyman-Scott process |
rMatClust | simulate the Mat'ern Cluster process |
rThomas | simulate the Thomas process |
rmh | simulate Gibbs point process using Metropolis-Hastings |
To randomly change an existing point pattern:
rlabel | random (re)labelling of a multitype point pattern |
rshift | random shift (including toroidal shifts) |
Standard point pattern datasets:
Remember to say data(bramblecanes)
etc.
amacrine | Austin Hughes' rabbit amacrine cells |
ants | Harkness-Isham ant nests data |
betacells | Waessle et al. cat retinal ganglia data |
bramblecanes | Bramble Canes data |
cells | Crick-Ripley biological cells data |
chorley | Chorley-Ribble cancer data |
copper | Berman-Huntington copper deposits data |
demopat | Synthetic point pattern |
finpines | Finnish Pines data |
hamster | Aherne's hamster tumour data |
humberside | North Humberside childhood leukaemia data |
japanesepines | Japanese Pines data |
lansing | Lansing Woods data |
longleaf | Longleaf Pines data |
nztrees | Mark-Esler-Ripley trees data |
redwood | Strauss-Ripley redwood saplings data |
redwoodfull | Strauss redwood saplings data (full set) |
residualspaper | Data from Baddeley et al (2005) |
simdat | Simulated point pattern (inhomogeneous, with interaction) |
spruces | Spruce trees in Saxonia |
swedishpines | Strand-Ripley swedish pines data |
To manipulate a point pattern:
plot.ppp | plot a point pattern (e.g. plot(X) ) |
subset.ppp , "[.ppp" | extract or replace a subset of a point pattern |
pp[subset] |
|
pp[, subwindow] |
|
superimpose | superimpose any number of point patterns |
cut.ppp | discretise the marks in a point pattern |
unmark | remove marks |
setmarks | attach marks or reset marks |
split.ppp | divide pattern into sub-patterns |
rotate | rotate pattern |
shift | translate pattern |
affine | apply affine transformation |
density.ppp | kernel smoothing |
identify.ppp | interactively identify points |
unique.ppp | remove duplicate points |
duplicated.ppp | determine which points are duplicates |
See spatstat.options
to control plotting behaviour.
To create a window:
An object of class "owin"
describes a spatial region
(a window of observation).
owin | Create a window object |
owin(xlim, ylim) for rectangular window |
|
owin(poly) for polygonal window |
|
owin(mask) for binary image window |
|
as.owin | Convert other data to a window object |
ripras | Ripley-Rasson estimator of window, given only the points |
letterR | polygonal window in the shape of the {sf R} logo |
To manipulate a window:
plot.owin | plot a window. |
plot(W) |
|
bounding.box | Find a tight bounding box for the window |
erode.owin | erode window by a distance r |
dilate.owin | dilate window by a distance r |
complement.owin | invert (swap inside and outside) |
rotate | rotate window |
shift | translate window |
affine | apply affine transformation |
Digital approximations:
as.mask | Make a discrete pixel approximation of a given window |
nearest.raster.point | map continuous coordinates to raster locations |
raster.x | raster x coordinates |
raster.y | raster y coordinates |
See spatstat.options
to control the approximation
Geometrical computations with windows:
intersect.owin | intersection of two windows |
union.owin | union of two windows |
inside.owin | determine whether a point is inside a window |
area.owin | compute window's area |
diameter | compute window frame's diameter |
eroded.areas | compute areas of eroded windows |
bdist.points | compute distances from data points to window boundary |
bdist.pixels | compute distances from all pixels to window boundary |
distmap.owin | distance transform image |
centroid.owin | compute centroid (centre of mass) of window |
is.subset.owin | determine whether one window contains another |
Pixel images:
An object of class "im"
represents a pixel image.
Such objects are returned by some of the functions in
spatstat
including Kmeasure
,
setcov
and density.ppp
.
im | create a pixel image |
as.im | convert other data to a pixel image |
plot.im | plot a pixel image on screen as a digital image |
contour.im | draw contours of a pixel image |
persp.im | draw perspective plot of a pixel image |
[.im | extract subset of pixel image |
shift.im | apply vector shift to pixel image |
X | print very basic information about image X |
summary(X) | summary of image X |
hist.im | histogram of image |
mean.im | mean pixel value of image |
is.im | test whether an object is a pixel image |
compatible.im | test whether two images have compatible dimensions |
eval.im | evaluate any expression involving images |
Line segment patterns
An object of class "psp"
represents a pattern of line
segments.
psp | create a line segment pattern |
as.psp | convert other data into a line segment pattern |
plot.psp | plot a line segment pattern |
print.psp | print basic information |
summary.psp | print summary information |
subset.psp | |
[.psp | extract a subset of a line segment pattern |
midpoints.psp | compute the midpoints of line segments |
endpoints.psp | extract the endpoints of line segments |
lengths.psp | compute the lengths of line segments |
angles.psp | compute the orientation angles of line segments |
rotate.psp | rotate a line segment pattern |
shift.psp | shift a line segment pattern |
affine.psp | apply an affine transformation |
distmap.psp | compute the distance map of a line segment pattern |
density.psp | kernel smoothing of line segments |
Inspection of data:
summary(X) | print useful summary of point pattern X |
X | print basic description of point pattern X |
quadratcount | Quadrat counts |
Summary statistics for a point pattern:
Fest | empty space function F |
Gest | nearest neighbour distribution function G |
Kest | Ripley's K-function |
Jest | J-function J = (1-G)/(1-F) |
pcf | pair correlation function |
Kinhom | K for inhomogeneous point patterns |
Kest.fft | fast K-function using FFT for large datasets |
Kmeasure | reduced second moment measure |
allstats | all four functions F, G, J, K |
envelope | simulation envelopes for a summary function |
Related facilities:
plot.fv | plot a summary function |
eval.fv | evaluate any expression involving summary functions |
nndist | nearest neighbour distances |
pairdist | distances between all pairs of points |
crossdist | distances between points in two patterns |
exactdt | distance from any location to nearest data point |
distmap | distance map image |
density.ppp | kernel smoothed density |
Summary statistics for a multitype point pattern:
A multitype point pattern is represented by an object X
of class "ppp"
with a component X$marks
which is a factor.
Gcross,Gdot,Gmulti | multitype nearest neighbour distributions Gij, Gi. |
Kcross,Kdot, Kmulti | multitype K-functions Kij, Ki. |
Jcross,Jdot,Jmulti | multitype J-functions Jij,Ji. |
alltypes | estimates of the above for all i,j pairs |
Iest | multitype I-function |
Summary statistics for a marked point pattern:
A marked point pattern is represented by an object X
of class "ppp"
with a component X$marks
.
The entries in the vector X$marks
may be numeric, complex,
string or any other atomic type.
markcorr | mark correlation function |
Gmulti | multitype nearest neighbour distribution |
Kmulti | multitype K-function |
Jmulti | multitype J-function |
Alternatively use cut.ppp
to convert a marked point pattern
to a multitype point pattern.
Programming tools:
applynbd | apply function to every neighbourhood |
in a point pattern |
To fit a point process model:
Model fitting in spatstat
is performed by the function
ppm
. Its result is an object of class "ppm"
.
Manipulating the fitted model:
plot.ppm | Plot the fitted model |
predict.ppm | Compute the spatial trend |
and conditional intensity | |
of the fitted point process model | |
coef.ppm | Extract the fitted model coefficients |
fitted.ppm | Compute fitted conditional intensity at quadrature points |
update.ppm | Update the fit |
rmh.ppm | Simulate from fitted model |
print.ppm | Print basic information about a fitted model |
summary.ppm | Summarise a fitted model |
anova.ppm | Analysis of deviance |
See spatstat.options
to control plotting of fitted model.
To specify a point process model:
The first order ``trend'' of the model is written as an R
language formula.
~1 | No trend (stationary) |
~x | First order term λ(x,y) = exp(α + β x) |
where x,y are Cartesian coordinates | |
~polynom(x,y,3) | Log-cubic polynomial trend |
~harmonic(x,y,2) | Log-harmonic polynomial trend |
The higher order (``interaction'') components are described by
an object of class "interact"
. Such objects are created by:
Poisson() | the Poisson point process |
Strauss() | the Strauss process |
StraussHard() | the Strauss/hard core point process |
Softcore() | pairwise interaction, soft core potential |
PairPiece() | pairwise interaction, piecewise constant |
DiggleGratton() | Diggle-Gratton potential |
LennardJones() | Lennard-Jones potential |
Pairwise() | pairwise interaction, user-supplied potential |
Geyer() | Geyer's saturation process |
Saturated() | Saturated pair model, user-supplied potential |
OrdThresh() | Ord process, threshold potential |
Ord() | Ord model, user-supplied potential |
MultiStrauss() | multitype Strauss process |
MultiStraussHard() | multitype Strauss/hard core process |
Finer control over model fitting:
A quadrature scheme is represented by an object of
class "quad"
.
quadscheme | generate a Berman-Turner quadrature scheme |
for use by ppm |
|
default.dummy | default pattern of dummy points |
gridcentres | dummy points in a rectangular grid |
stratrand | stratified random dummy pattern |
spokes | radial pattern of dummy points |
corners | dummy points at corners of the window |
gridweights | quadrature weights by the grid-counting rule |
dirichlet.weights | quadrature weights are Dirichlet tile areas |
plot(Q) | plot quadrature scheme Q |
print(Q) | print basic information about quadrature scheme Q |
summary(Q) | summary of quadrature scheme Q |
Simulation and goodness-of-fit:
rmh.ppm | simulate realisations of a fitted model |
envelope | compute simulation envelopes for a fitted model |
Diagnostic plots:
Type demo(diagnose)
for a demonstration of the diagnostics features.
diagnose.ppm | diagnostic plots for spatial trend |
qqplot.ppm | diagnostic plot for interpoint interaction |
The online manual entries are quite detailed and should be consulted first for information about a particular function.
The paper by Baddeley and Turner (2005a) describes the package. Baddeley and Turner (2005b) is a more detailed explanation of how to fit point process models to data.
This library and its documentation are usable under the terms of the "GNU General Public License", a copy of which is distributed with the package.
Marie-Colette van Lieshout made substantial contributions of code. Contributions were also made by J.B. Chen, Y.C. Chin, S. Eglen, P. Grabarnik, U. Hahn, M.B. Hansen, K. Hornik, J. Mateu, L.S. Nielsen, B.D. Ripley, B. Rowlingson, A. Sarkka, K. Schladitz, B.T. Scott, M. Stevenson, B. Turlach, and A. van Burgel.
Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner rolf@math.unb.ca http://www.math.unb.ca/~rolf
Baddeley, A. and Turner, R. (2005a)
Spatstat: an R package for analyzing spatial point patterns.
Journal of Statistical Software 12:6, 1–42.
URL: www.jstatsoft.org
, ISSN: 1548-7660.
Baddeley, A. and Turner, R. (2005b) Modelling spatial point patterns in R. In: A. Baddeley, P. Gregori, J. Mateu, R. Stoica, and D. Stoyan, editors, Case Studies in Spatial Point Pattern Modelling, Lecture Notes in Statistics number 185. Pages 23–74. Springer-Verlag, New York, 2006. ISBN: 0-387-28311-0.
Baddeley, A., Turner, R., Moller, J. and Hazelton, M. (2005) Residual analysis for spatial point processes. Journal of the Royal Statistical Society, Series B 67, 617–666.