plot.tile.list: Plot Dirichlet (Voronoi) tiles

In deldir: Delaunay Triangulation and Dirichlet (Voronoi) Tessellation

Plot Dirichlet (Voronoi) tiles

Description

A method for plot. Plots (sequentially) the tiles associated with each point in the set being tessellated.

Usage

## S3 method for class 'tile.list'
plot(x, verbose = FALSE, close = FALSE, pch = 1,
                         fillcol = getCol(x,warn=warn), col.pts=NULL,
                         col.lbls=NULL,border=NULL, showpoints = !labelPts,
                         add = FALSE, asp = 1, clipp=NULL, xlab = "x",
                         ylab = "y", main = "", warn=TRUE,
                         labelPts=FALSE,adj=NULL,...) 

Arguments

x	A list of the tiles in a tessellation, as produced the function tile.list().
verbose	Logical scalar; if TRUE the tiles are plotted one at a time (with a “Go?” prompt after each) so that the process can be watched.
close	Logical scalar; if TRUE the outer edges of of the tiles (i.e. the edges which are constitute parts of the edges of the enclosing rectangle) are drawn. Otherwise tiles on the periphery of the tessellation are left “open”.
pch	The plotting character (or vector of plotting characters) with which to plot the points of the pattern which was tessellated. Ignored if showpoints is FALSE.
fillcol	Optional vector (possibly of length 1, i.e. a scalar) whose entries can be interpreted as colours by col2rgb(). The i-th entry indicates with which colour to fill the i-th tile. Note that an NA entry cause the tile to be left unfilled. This argument will be replicated to have length equal to the number of tiles. The default value is created (using the tile “tags”, i.e. the z components of the tiles, if these exist) by the undocumented function getCol(). Note that if these z components are not present, then getCol() returns NA.
col.pts	Optional vector like unto fillcol whose entries can be interpreted as colours by col2rgb(). The i-th entry indicates with which colour to plot the i-th point. This argument will be replicated to have length equal to the number of tiles. Ignored if showpoints is FALSE.
col.lbls	Optional vector like unto col.pts. Determines the colours in which the point labels (see labelPts below) are plotted. This argument will be replicated to have length equal to the number of tiles. Ignored if labelPts is FALSE.
border	A scalar that can be interpreted as a colour by col2rgb(), indicating the colour with which to plot the tile boundaries. Defaults to black unless all of the fill colours specified by fillcol are black, in which case it defaults to white. If length(border) > 1 then only its first entry is used.
showpoints	Logical scalar; if TRUE the points of the pattern which was triangulated/tessellated are plotted. If clipp is specified, then only those points associated with non-empty clipped tiles are shown. Note that some such points will be external to the polygon clipp and that these “external” points are shown.
add	Logical scalar; should the plot of the tiles be added to an existing plot?
asp	The aspect ratio of the plot; integer scalar or NA. Set this argument equal to NA to allow the data to determine the aspect ratio and hence to make the plot occupy the complete plotting region in both x and y directions. This is inadvisable; see the Warnings.
clipp	An object specifying a polygon to which the tessellation being plotted should be clipped. It should consist either of: a list containing two components x and y giving the coordinates of the vertices of a single polygon. The last vertex should not repeat the first vertex. Or: a list of list(x,y) structures giving the coordinates of the vertices of several polygons. If this argument is provided then the plot of the tessellation is “clipped” to the polygon specified by clipp.
xlab	Label for the x-axis (used only if add is FALSE).
ylab	Label for the y-axis (used only if add is FALSE).
main	A title for the plot (used only if add is FALSE).
warn	Logical scalar passed to the internal function getCol(). Should a warning be issued if the z components of the entries of x cannot all be interpreted as colours? (See Notes.)
labelPts	Logical scalar; if TRUE the labels of the points determining the tiles are plotted in the tiles. Note that if labelPts is TRUE then showpoints defaults to FALSE
adj	The “adjustment” argument to text(). If labelPts and showpoints are both TRUE it defaults to -1 (so that the labels and point symbols are not superimposed). If labelPts is TRUE and showpoints is FALSE it defaults to 0. If labelPts is FALSE it is ignored.
...	Optional arguments; may be passed to points() and text().

Value

The list of tiles being plotted. This will be the input list of tiles specified by argument x, or this list clipped to the polygon clipp if the latter was specified.

Warnings

• As of release 1.0-8 the argument number of plot.deldir() and plot.tile.list() was changed to labelPts. As a consequence the argument col.num of this function has had its name changed to col.lbls.

• The behaviour of this function with respect to “clipping” has changed substantially since the previous release of deldir, i.e. 1.1-0. The argument clipwin has been re-named clipp (“p” for “polygon”). Clipping is now effected via the new package polyclip. The spatstat package is no longer used. The argument use.gpclib has been eliminated, since gpclib (which used to be called upon by spatstat has been superseded by polyclip which has an unrestrictive license.

• As of release 0.1-1 of the deldir package, the argument fillcol to this function replaces the old argument polycol, but behaves somewhat differently.

• The argument showrect which was present in versions of this function prior to release 0.1-1 has been eliminated. It was redundant.

• As of release 0.1-1 the col.pts argument might behave somewhat differently from how it behaved in the past.

• The arguments border, clipp, and warn are new as of release 0.1-1.

• Users, unless they really understand what they are doing and why they are doing it, are strongly advised not to set the value of asp but rather to leave asp equal to its default value of 1. Any other value distorts the tesselation and destroys the perpendicular appearance of lines which are indeed perpendicular. (And conversely can cause lines which are not perpendicular to appear as if they are.)

Notes

• If clipp is not NULL and showpoints is TRUE then it is possible that some of the points “shown” will not fall inside any of the plotted tiles. (This will happen if the parts of the tiles in which they fall have been “clipped” out.) If a tile is clipped out completely then the point which determines that tile is not plotted irrespective of the value of showpoints.

• If the z components of the entries of x exist but cannot all be interpreted as colours then the internal function getCol() returns NA. If warn is TRUE then a warning is issued. The function getCol() will also return NA (no warning is issued in this case) if there aren't any z components. This circumstance will arise if no z argument was supplied in the call to deldir(). An NA value of fillcol results (as is indicated by the argument list entry for fillcol) in (all of) the tiles being left unfilled.

• The change from argument polycol to argument fillcol, and the resulting change in the way in which plotted tiles are filled with colours, was made as a result of a request from Chris Triggs. Likewise the argument clipp was added due to a request from Chris Triggs.

• The argument asp was added at the request of Zubin Dowlaty (who presumably knows what he's doing!).

Author(s)

\rolf

See Also

deldir(), tile.list(), triang.list(), plot.triang.list()

Examples

  set.seed(42)
  x <- runif(20)
  y <- runif(20)
  z <- deldir(x,y,rw=c(0,1,0,1))
  w <- tile.list(z)
  plot(w)
  ccc <- heat.colors(20) # Or topo.colors(20), or terrain.colors(20)
                         # or cm.colors(20), or rainbow(20).
  plot(w,fillcol=ccc,close=TRUE)
  if(require(polyclip)) {
     CP  <- list(x=c(0.49,0.35,0.15,0.20,0.35,0.42,
                     0.43,0.62,0.46,0.63,0.82,0.79),
                 y=c(0.78,0.86,0.79,0.54,0.58,0.70,
                     0.51,0.46,0.31,0.20,0.37,0.54))
     cul <- rainbow(10)[c(1,7,3:6,2,8:10)] # Rearranging colours to improve
                                           # the contrast between contiguous tiles.
     plot(w,clipp=CP,showpoints=FALSE,fillcol=cul)
  }
  plot(w,labelPts=TRUE,col.lbls="red")
  plot(w,labelPts=TRUE,col.lbls="red",cex=0.5)
  plot(w,showpoints=TRUE,labelPts=TRUE,col.pts="green",col.lbls="red")

deldir documentation built on Nov. 23, 2023, 9:09 a.m.