Define the coordinates of one or more straight lines in the plane
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, …)
Numeric vectors of equal length giving the
intercepts \(a\) and slopes \(b\) of the lines.
Incompatible with h,v,p,theta
Numeric vector giving the positions of horizontal lines when
they cross the \(y\) axis.
Incompatible with a,b,v,p,theta
Numeric vector giving the positions of vertical lines when
they cross the \(x\) axis.
Incompatible with a,b,h,p,theta
Numeric vectors of equal length
giving the polar coordinates of the line.
Incompatible with a,b,h,v
An object of class "infline"
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.
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.
# 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)))
# }
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