# plot.ppp

##### plot a Spatial Point Pattern

Plot a two-dimensional spatial point pattern

##### Usage

```
## S3 method for class 'ppp':
plot(x, main, \dots, chars=NULL, cols=NULL,
use.marks=TRUE, which.marks=1, add=FALSE,
maxsize=NULL, markscale=NULL,zap=0.01)
```

##### Arguments

- x
- The spatial point pattern to be plotted.
An object of class
`"ppp"`

, or data which can be converted into this format by`as.ppp()`

. - main
- text to be displayed as a title above the plot.
- ...
- extra arguments that will be passed to the plotting functions
`plot.default`

,`points`

and/or`symbols`

- chars
- plotting character(s) used to plot points.
- cols
- the colour(s) used to plot points.
- use.marks
- logical flag; if
`TRUE`

, plot points using a different plotting symbol for each mark; if`FALSE`

, only the locations of the points will be plotted, using`points()`

. - which.marks
- Index determining which column of marks to use,
if the marks of
`x`

are a data frame. A character string or an integer. Defaults to`1`

indicating the first column of marks. - add
- logical flag; if
`TRUE`

, just the points are plotted, over the existing plot. A new plot is not created, and the window is not plotted. - maxsize
- maximum size of the circles/squares plotted
when
`x`

is a marked point pattern with numerical marks. Incompatible with`markscale`

. - markscale
- physical scale factor determining the sizes of the
circles/squares plotted when
`x`

is a marked point pattern with numerical marks. Incompatible with`maxsize`

. - zap
- Fraction between 0 and 1.
When
`x`

is a marked point pattern with numerical marks,`zap`

is the smallest mark value (expressed as a fraction of the maximum possible mark) that will be plotted. Any points which ha

##### Details

This is the `plot`

method for
point pattern datasets (of class `"ppp"`

, see `ppp.object`

).

First the observation window `x$window`

is plotted.
Then the points themselves are plotted,
in a fashion that depends on their marks,
as follows.
[object Object],[object Object],[object Object],[object Object]

Plotting of the window `x$window`

is performed by
`plot.owin`

. This plot may be modified
through the `...`

arguments. In particular the
extra argument `border`

determines
the colour of the window.

Plotting of the points themselves is performed
by the function `points`

, except for the case of
continuous marks, where it is performed by `symbols`

.
Their plotting behaviour may be modified through the `...`

arguments.

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(x$marks)`

, 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, or a
marked point pattern with continuous marks, this 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(x$marks)`

. The $i$th level or type will
be plotted using colour `cols[i]`

.

If `cols`

is absent, the colour used to plot *all* the
points may be determined by the extra argument `fg`

(for multitype point patterns) or the extra argument `col`

(for all other cases). Note that `col`

will also reset the
colour of the window.

The arguments `maxsize`

and `markscale`

incompatible. They control the physical size of the circles and
squares which represent the marks in a point pattern with continuous
marks. If `markscale`

is given, then a mark value of `m`

is plotted as a circle of radius `m * markscale`

(if `m`

is positive) or a square of side `abs(m) * markscale`

(if `m`

is negative). If `maxsize`

is given, then the
largest mark in absolute value, `mmax=max(abs(x$marks))`

,
will be scaled to have physical size `maxsize`

.

The user can set the default values of these plotting parameters
using `spatstat.options("par.points")`

.
To zoom in (to view only a subset of the point pattern at higher
magnification), use the graphical arguments
`xlim`

and `ylim`

to specify the rectangular field of view.

The value returned by this plot function can be used to make a suitable legend, as shown in the examples.

##### Value

`NULL`

, or a vector giving the correspondence between mark values and plotting characters.

##### Removing White Space Around The Plot

A frequently-asked question is: How do I remove the white space around
the plot? Currently `plot.ppp`

uses the base graphics system of
R, so the space around the plot is controlled by parameters
to `par`

. To reduce the white space, change the
parameter `mar`

. Typically, `par(mar=rep(0.5, 4))`

is
adequate, if there are no annotations or titles outside the window.

##### See Also

##### Examples

```
data(cells)
plot(cells)
plot(cells, pch=16)
# make the plotting symbols larger (for publication at reduced scale)
plot(cells, cex=2)
# set it in spatstat.options
oldopt <- spatstat.options(par.points=list(cex=2))
plot(cells)
spatstat.options(oldopt)
# multitype
data(lansing)
plot(lansing)
# marked by a real number
data(longleaf)
plot(longleaf)
# just plot the points
plot(longleaf, use.marks=FALSE)
plot(unmark(longleaf)) # equivalent
# controlling COLOURS of points
plot(cells, cols="blue")
plot(lansing, cols=c("black", "yellow", "green",
"blue","red","pink"))
plot(longleaf, fg="blue")
# make window purple
plot(lansing, border="purple")
# make everything purple
plot(lansing, border="purple", cols="purple", col.main="purple")
# controlling PLOT CHARACTERS
plot(lansing, chars = 11:16)
plot(lansing, chars = c("o","h","m",".","o","o"))
# controlling MARK SCALE
plot(longleaf, markscale=0.1)
# draw circles of DIAMETER equal to nearest neighbour distance
plot(cells %mark% nndist(cells), markscale=1/2)
# making the legend
data(amacrine)
v <- plot(amacrine)
legend(0.2, 1.2, pch=v, legend=names(v))
# point pattern with multiple marks
data(finpines)
plot(finpines, which.marks="height")
```

*Documentation reproduced from package spatstat, version 1.31-3, License: GPL (>= 2)*