Determines a symbol map for plotting the spatial point pattern x.
# S3 method for ppp
default.symbolmap(x, ...,
chars = NULL, cols = NULL,
fixsize = FALSE,
maxsize = NULL, meansize = NULL, markscale = NULL,
minsize = NULL, zerosize = NULL, transform = NULL)A symbol map (object of class "symbolmap")
or a list of symbol maps, one for each column of marks.
This algorithm determines a symbol map that can be used to
represent the points of x graphically.
It serves as the default symbol map for the plot method
plot.ppp.
Users can modify the behaviour of plot.ppp by
saving the symbol map produced by default.symbolmap.ppp,
modifying the symbol map using update.symbolmap or other
tools, and passing the modified symbol map to plot.ppp
as the argument symap.
The default representation depends on the marks of the points, as follows.
If the point pattern does not have marks, then every point will be represented by the same plot symbol.
If marks(x) is a factor, then
each level of the factor is
represented by a different plot character.
If marks(x) is a numeric vector,
each point is represented by a circle
with diameter proportional to the mark
(if the value is positive) or a square with side length
proportional to the absolute value of the mark
(if the value is negative).
If marks(x) is neither numeric nor a factor,
then each possible mark will be represented by a
different plotting character. The default is to
represent the \(i\)th smallest mark value by
points(..., pch=i).
The following arguments can be used to modify how the points are plotted:
If fixsize=TRUE, or if the graphics parameter size is
given and is a single value, then numerical marks will be rendered
as symbols of the same physical size
The argument chars determines the plotting character
or characters used to display the points (in all cases except
for the case of continuous marks). For an unmarked point pattern,
this should be a single integer or character determining a
plotting character (see par("pch")).
For a multitype point pattern, chars should be a vector
of integers or characters, of the same length
as levels(marks(x)), and then the \(i\)th level or type
will be plotted using character chars[i].
If chars is absent, but there is an extra argument
pch, then this will determine the plotting character for
all points.
The argument cols determines the colour or colours used to
display the points. For an unmarked point pattern,
cols should be a character string
determining a colour. For a multitype point pattern, cols
should be a character vector, of the same length
as levels(marks(x)): that is, there is one colour for each
possible mark value. The \(i\)th level or type will
be plotted using colour cols[i]. For a point pattern with
continuous marks, cols can be either a character string
or a character vector specifying colour values: the range of mark
values will be mapped to the specified colours.
Alternatively, for any kind of data, cols can be a colour map
(object of class "colourmap") created by colourmap.
If cols is absent, the colours used to plot the
points may be determined by the extra arguments fg
and bg for foreground (edge) and background (fill) colours.
(These parameters are not recommended for plotting
multitype point patterns, due to quirks of the graphics system.)
The default colour for the points is a semi-transparent grey,
if this is supported by the plot device. This behaviour can be
suppressed (so that the default colour is non-transparent)
by setting spatstat.options(transparent=FALSE).
The arguments maxsize, meansize and markscale
are incompatible with each other (and incompatible with
symap).
The arguments minsize and zerosize are incompatible
with each other (and incompatible with symap).
Together, these arguments control the physical size of the circles and
squares which represent the marks in a point pattern with continuous
marks. The size of a circle is defined as its diameter;
the size of a square is its side length.
If markscale is given, then a mark value of m
is plotted as a circle of diameter m * markscale + zerosize
(if m is positive) or a square of side
abs(m) * markscale + zerosize
(if m is negative). If maxsize is given, then the
largest mark in absolute value, mmax=max(abs(marks(x))),
will be scaled to have physical size maxsize.
If meansize is given, then the
average absolute mark value, mmean=mean(abs(marks(x))),
will be scaled to have physical size meansize.
If minsize is given, then the
minimum mark value, mmean=mean(abs(marks(x))),
will be scaled to have physical size minsize.
The user can set the default values of these plotting parameters
using spatstat.options("par.points").
Additionally the user can specify any of the graphics parameters
recognised by symbolmap, including
shape, size, pch, cex,
cols, col, fg, bg,
lwd, lty, etch,
direction,headlength,headangle,arrowtype.
plot.ppp
default.symbolmap
symbolmap
default.symbolmap(longleaf)
default.symbolmap(lansing)
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