cetaceans: Point patterns of whale and dolphin sightings.

In spatstat.data: Datasets for 'spatstat' Family

Point patterns of whale and dolphin sightings.

Description

Nine (independent replicate) point patterns of whale and dolphin sightings obtained from aircraft flying along eight parallel transects in the region of Great Barrier Island, the Hauraki Gulf and the Coromandel Peninsula (New Zealand). Most of the transects are interrupted by portions of land mass. Observations were recorded within narrow rectangles of total width 840 metres (420 metres on each side of the transect).

Usage

   data(cetaceans)

Format

The object cetaceans is a hyperframe (see hyperframe()) with 9 rows and 4 columns. Each row of this hyperframe represents a replicate survey. The columns are whales, dolphins, fish and plankton.

Each entry in the hyperframe is a point pattern. The dolphins column consists of marked patterns (with marks having levels dd and tt) while the other columns contain unmarked point patterns.

The object cetaceans.extra is a list containing auxiliary data. It currently contains only one entry, patterns, which contains the same information as cetaceans in another form. This is a list, of class solist (“spatial object list”; see solist(), as.solist()). It is a list of length 9, in which each entry is a marked point pattern, representing the result of one survey. Each pattern was obtained by superimposing the whales, dolphins, fish and plankton patterns from the corresponding row of cetaceans. The marks of these patterns have levels be, dd, fi, tt and zo.

Details

The data were obtained from nine aerial surveys, conducted from 02/12/2013 to 22/04/2014. Each survey was conducted over the course of a single day. The gap between successive surveys ranged from two to six weeks (making it “not unreasonable” to treat the patterns obtained as being independent). The marks of the patterns referred to above may be interpreted as follows:

• be: whales — Bryde's whale (Balaenoptera edeni)

• dd: dolphins — Common dolphin (Delphinus delphis)

• fi: fish — Any species that forms schools

• tt: dolphins — Bottlenose dolphin (Tursiops truncatus)

• zo: plankton — Zooplankton

The window for the point patterns in these data sets is of type polygonal and consists of a number of thin rectangular strips. These are arranged along eight parallel transects.

The units in which the patterns are presented are kilometres.

These data are rather “sparse”. For example there are a total of only eight whale observations in the entire data set (all nine surveys). Thus conclusions drawn from these data should be treated with even more than the usual amount of circumspection.

Source

These data were kindly supplied by Lily Kozmian-Ledward, who studied them in the course of writing her Master's thesis at the University of Auckland, under the joint supervision of Dr. Rochelle Constantine, University of Auckland and Dr Leigh Torres, Oregon State University.

References

Kozmian-Ledward, L. (2014). Spatial ecology of cetaceans in the Hauraki Gulf, New Zealand. Unpublished MSc thesis, University of Auckland, New Zealand.

Examples

  if(require(spatstat.model)) {
     cet <- cetaceans
     cet$dMplank <- with(cet, distfun(plankton, undef=20))
     cet$dMfish <- with(cet, distfun(fish, undef=20))
     fit.whales <- mppm(whales ~ dMplank + dMfish,data=cet)
     anova(fit.whales,test="Chi")
     # Note that inference is *conditional* on the fish and
     # plankton patterns.
     cetPats <- cetaceans.extra$patterns
     plot(Window(cetPats[[1]]),main="The window")
     plot(cetPats,nrows=3,main="All data")
  }

spatstat.data documentation built on May 29, 2024, 9:10 a.m.