# ants

##### Harkness-Isham ants' nests data

These data give the spatial locations of nests of two species of
ants, *Messor wasmanni* and *Cataglyphis bicolor*,
recorded by Professor R.D. Harkness at a site in northern Greece,
and described in Harkness & Isham (1983).
The full dataset (supplied here) has an irregular polygonal boundary,
while most analyses have been confined to two rectangular
subsets of the pattern (also supplied here).

The harvester ant *M. wasmanni*
collects seeds for food and builds a nest composed mainly of
seed husks. *C. bicolor* is a heat-tolerant desert foraging ant which
eats dead insects and other arthropods. Interest focuses on whether
there is evidence in the data for intra-species competition
between *Messor* nests (i.e. competition for resources) and for
preferential placement of *Cataglyphis* nests in the vicinity of
*Messor* nests.

The full dataset is displayed in Figure 1 of Harkness & Isham (1983).
See **Usage** below to produce a comparable plot.
It comprises 97 nests (68 Messor and 29 Cataglyphis)
inside an irregular convex polygonal boundary, together with
annotations showing a foot track through the region,
the boundary between field and scrub areas inside the
region, and indicating the two rectangular subregions
A and B used in their analysis.
Rectangular subsets of the data were analysed by
Harkness & Isham (1983), Isham (1984), Takacs & Fiksel
(1986), S"arkk"a (1993, section 5.3),
H"ogmander and S"arkk"a (1999) and Baddeley & Turner (2000).
The full dataset (inside its irregular boundary) was first analysed
by Baddeley & Turner (2005b).
The dataset `ants`

is the full point pattern
enclosed by the irregular polygonal boundary.
The $x$ and $y$ coordinates are eastings (E-W) and northings (N-S)
scaled so that 1 unit equals 0.5 feet.
This is a multitype point pattern object, each point carrying a mark
indicating the ant species (with levels `Cataglyphis`

and `Messor`

).

The dataset `ants.extra`

is a list of auxiliary
information:
[object Object],[object Object],[object Object],[object Object],[object Object]

##### Usage

`data(ants)`

##### source

Harkness and Isham (1983). Nest coordinates kindly provided by Prof Valerie Isham. Polygon coordinates digitised by Adrian Baddeley from a reprint of Harkness & Isham (1983).

##### References

Baddeley, A. and Turner, R. (2000)
Practical maximum pseudolikelihood for spatial point patterns.
*Australian and New Zealand Journal of Statistics*
**42**, 283--322.
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.

Harkness, R.D. and Isham, V. (1983)
A bivariate spatial point pattern of ants' nests.
*Applied Statistics* **32**, 293--303.

H"ogmander, H. and S"arkk"a, A. (1999)
Multitype spatial point patterns with hierarchical interactions.
*Biometrics* **55**, 1051--1058.

Isham, V.S. (1984)
Multitype Markov point processes: some approximations.
*Proceedings of the Royal Society of London, Series A*,
**391**, 39--53.

Takacs, R. and Fiksel, T. (1986)
Interaction pair-potentials for a system of ants' nests.
*Biometrical Journal* **28**, 1007--1013.

S"arkk"a, A. (1993)
*Pseudo-likelihood approach for pair potential
estimation of Gibbs processes*.
Number 22 in Jyv"askyl"a Studies in Computer Science, Economics
and Statistics. University of Jyv"askyl"a, Finland.

##### Examples

```
# Equivalent to Figure 1 of Harkness and Isham (1983)
data(ants)
ants.extra$plotit()
# Data in subrectangle A, rotated
# Approximate data used by Sarkka (1993)
angle <- atan(diff(ants.extra$fieldscrub$y)/diff(ants.extra$fieldscrub$x))
plot(rotate(ants.extra$A, -angle))
# Approximate window used by Takacs and Fiksel (1986)
tfwindow <- bounding.box(ants$window)
antsTF <- ppp(ants$x, ants$y, window=tfwindow)
plot(antsTF)
```

*Documentation reproduced from package spatstat, version 1.31-3, License: GPL (>= 2)*