R: Plot Dirichlet (Voronoi) tiles

plot.tile.list {deldir}

R Documentation

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 = "", axes=TRUE,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`).
`axes`	Logical scalar. Should axes (with a marked numeric scale) be plotted? This argument is used only if `add` is `FALSE`. It allows the plotting of such axes to be suppressed. The argument was added at the request of Damon Tutunjian. To suppress the plotting of axis labels set `xlab=""` and/or `ylab=""`.
`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.) The argument asp was added at the request of Zubin Dowlaty (who presumably knows what he's doing!).

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.

Author(s)

Rolf Turner rolfurner@posteo.net

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")
  plot(w,axes=FALSE,xlab="",ylab="",close=TRUE)

[Package deldir version 2.0-4 Index]