# infline

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##### Infinite Straight Lines

Define the coordinates of one or more straight lines in the plane

Keywords
spatial, datagen
##### Usage
infline(a = NULL, b = NULL, h = NULL, v = NULL, p = NULL, theta = NULL)# S3 method for infline
print(x, …)# S3 method for infline
plot(x, …)
##### Arguments
a,b

Numeric vectors of equal length giving the intercepts $a$ and slopes $b$ of the lines. Incompatible with h,v,p,theta

h

Numeric vector giving the positions of horizontal lines when they cross the $y$ axis. Incompatible with a,b,v,p,theta

v

Numeric vector giving the positions of vertical lines when they cross the $x$ axis. Incompatible with a,b,h,p,theta

p,theta

Numeric vectors of equal length giving the polar coordinates of the line. Incompatible with a,b,h,v

x

An object of class "infline"

Extra arguments passed to print for printing or abline for plotting

##### Details

The class infline is a convenient way to handle infinite straight lines in the plane.

The position of a line can be specified in several ways:

• its intercept $a$ and slope $b$ in the equation $y = a + b x$ can be used unless the line is vertical.

• for vertical lines we can use the position $v$ where the line crosses the $y$ axis

• for horizontal lines we can use the position $h$ where the line crosses the $x$ axis

• the polar coordinates $p$ and $\theta$ can be used for any line. The line equation is $$y \cos\theta + x \sin\theta = p$$

The command infline will accept line coordinates in any of these formats. The arguments a,b,h,v have the same interpretation as they do in the line-plotting function abline.

The command infline converts between different coordinate systems (e.g. from a,b to p,theta) and returns an object of class "infline" that contains a representation of the lines in each appropriate coordinate system. This object can be printed and plotted.

##### Value

The value of infline is an object of class "infline" which is basically a data frame with columns a,b,h,v,p,theta. Each row of the data frame represents one line. Entries may be NA if a coordinate is not applicable to a particular line.

rotate.infline, clip.infline, chop.tess, whichhalfplane

##### Aliases
• infline
• plot.infline
• print.infline
##### Examples
# NOT RUN {
infline(a=10:13,b=1)
infline(p=1:3, theta=pi/4)
plot(c(-1,1),c(-1,1),type="n",xlab="",ylab="", asp=1)
plot(infline(p=0.4, theta=seq(0,pi,length=20)))
# }

Documentation reproduced from package spatstat, version 1.55-1, License: GPL (>= 2)

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