R: Interactively Define a Polygon

clickpoly {spatstat.geom} | R Documentation

## Interactively Define a Polygon

### Description

Allows the user to create a polygon by point-and-click in the display.

### Usage

      clickpoly(add=FALSE, nv=NULL, np=1, ...)

### Arguments

`add` | Logical value indicating whether to create a new plot (`add=FALSE`) or draw over the existing plot (`add=TRUE`).
`nv` | Number of vertices of the polygon (if this is predetermined).
`np` | Number of polygons to create.
`...` | Arguments passed to `locator` to control the interactive plot, and to `polygon` to plot the polygons.

### Details

This function allows the user to create a polygonal window by interactively clicking on the screen display.

The user is prompted to point the mouse at any desired locations for the polygon vertices, and click the left mouse button to add each point. Interactive input stops after `nv` clicks (if `nv` was given) or when the middle mouse button is pressed.

The return value is a window (object of class `"owin"`) representing the polygon.

This function uses the R command `locator` to input the mouse clicks. It only works on screen devices such as ‘X11’, ‘windows’ and ‘quartz’. Arguments that can be passed to `locator` through `...` include `pch` (plotting character), `cex` (character expansion factor) and `col` (colour). See `locator` and `par`.

Multiple polygons can also be drawn, by specifying `np > 1`. The polygons must be disjoint. The result is a single window object consisting of all the polygons.

### Value

A window (object of class `"owin"`) representing the polygon.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au and Rolf Turner r.turner@auckland.ac.nz.

### See Also

`identify.ppp`, `clickbox`, `clickppp`, `clickdist`, `locator`

[Package spatstat.geom version 2.2-0 Index]