redwoodfull: California Redwoods Point Pattern (Entire Dataset)

In spatstat.data: Datasets for 'spatstat' Family

California Redwoods Point Pattern (Entire Dataset)

Description

These data represent the locations of 195 seedlings and saplings of California Giant Redwood (Sequoiadendron giganteum) in a square sampling region.

They were described and analysed by Strauss (1975). This is the “full” dataset; most writers have analysed a subset extracted by Ripley (1977) which is available as redwood.

Strauss (1975) divided the sampling region into two subregions I and II demarcated by a diagonal line. The spatial pattern appears to be slightly regular in region I and strongly clustered in region II.

Strauss (1975) writes: “It was felt that the seedlings would be scattered fairly randomly, except that a number of tight clusters would form around some of the redwood tree stumps present in the plot. A discontinuity in the soil, very roughly demarked by the diagonal line in the figure, was expected to cause a difference in clustering behaviour between regions I and II. Moreover, almost all the redwood stumps were situated in region II.”

The dataset redwoodfull contains the full point pattern of 195 trees. The window has been rescaled to the unit square. Its physical size is approximately 130 feet across.

The auxiliary information about the subregions is contained in redwoodfull.extra, which is a list with entries

rdiag	The coordinates of the diagonal boundary
	between regions I and II
regionI	Region I as a window object
regionII	Region II as a window object
regionR	Ripley's subrectangle (approximate)
plotit	Function to plot the full data and auxiliary markings

Ripley (1977) extracted a subset of these data, containing 62 points, lying within a square subregion which overlaps regions I and II. He rescaled that subset to the unit square. This subset has been re-analysed many times, and is the dataset usually known as “the redwood data” in the spatial statistics literature. The exact dataset used by Ripley is supplied in the spatstat library as redwood.

The approximate position of the square chosen by Ripley within the redwoodfull pattern is indicated by the window redwoodfull.extra$regionR. There are some minor inconsistencies with redwood since it originates from a different digitisation.

Usage

data(redwoodfull)

Format

The dataset redwoodfull is an object of class "ppp" representing the point pattern of tree locations. See ppp.object for details of the format of a point pattern object. The window has been rescaled to the unit square. Its physical size is approximately 128 feet across.

The dataset redwoodfull.extra is a list with entries

rdiag	coordinates of endpoints of a line,
	in format list(x=numeric(2),y=numeric(2))
regionI	a window object
regionII	a window object
regionR	a window object
plotit	Function with no arguments

Source

Strauss (1975). The plot of the data published by Strauss (1975) was scanned and digitised by Sandra Pereira, University of Western Australia, 2002.

References

Diggle, P.J. (1983) Statistical analysis of spatial point patterns. Academic Press.

Ripley, B.D. (1977) Modelling spatial patterns (with discussion). Journal of the Royal Statistical Society, Series B 39, 172–212.

Strauss, D.J. (1975) A model for clustering. Biometrika 62, 467–475.

See Also

redwood

Examples

       data(redwoodfull)
  if(require(spatstat.geom)) {
       plot(redwoodfull)
       redwoodfull.extra$plotit()
       # extract the pattern in region II 
       redwoodII <- redwoodfull[, redwoodfull.extra$regionII]
   }

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