spatstat (version 1.48-0)

waterstriders: Waterstriders data. Three independent replications of a point pattern formed by insects.

Description

The territorial behaviour of an insect group called waterstriders was studied in a series of laboratory experiments by Dr Matti Nummelin (University of Helskini). The data were analysed in the pioneering PhD thesis of Antti Penttinen (1984).

The dataset waterstriders is a list of three point patterns. Each point pattern gives the locations of larvae of the waterstrider Limnoporus (Gerris) rufoscutellatus (larval stage V) in a homogeneous area about 48 cm square. The point patterns can be assumed to be independent.

It is known that this species of waterstriders exhibits territorialism at older larvae stages and at the adult stage. Therefore, if any deviation from Complete Spatial Randomness exists in these three point patterns, it is expected to be towards inhibition.

The data were obtained from photographs which were scanned manually. The waterstriders are in a pool which is larger than the picture. A guard area (width about 2.5 cm) has been deleted because it is a source of inhomogeneity to interactions.

Penttinen (1984, chapter 5) fitted a pairwise interaction model with a Strauss/hardcore interaction (see StraussHard) with hard core radius 1.5 cm and interaction radius 4.5 cm.

Usage

data(waterstriders)

Format

waterstriders is a list of three point patterns (objects of class "ppp"). It also has class "listof" so that it can be plotted and printed directly. The point pattern coordinates are in centimetres.

Source

Data were collected by Dr. Matti Nummelin (University of Helsinki, Finland). Data kindly provided by Prof. Antti Penttinen, University of Jyv\"askyl\"a, Finland.

References

Penttinen, A. (1984) Modelling interaction in spatial point patterns: parameter estimation by the maximum likelihood method. Jyv\"askyl\"a Studies in Computer Science, Economics and Statistics 7, University of Jyv\"askyl\"a, Finland.