Inversion | R Documentation |
An inversion is given by a pole (a point) and a power (a number, possibly negative, but not zero).
pole
get or set the pole
power
get or set the power
new()
Create a new Inversion
object.
Inversion$new(pole, power)
pole
the pole
power
the power
A new Inversion
object.
print()
Show instance of an inversion object.
Inversion$print(...)
...
ignored
Inversion$new(c(0,0), 2)
invert()
Inversion of a point.
Inversion$invert(M)
M
a point or Inf
A point or Inf
, the image of M
.
transform()
An alias of invert
.
Inversion$transform(M)
M
a point or Inf
A point or Inf
, the image of M
.
invertCircle()
Inversion of a circle.
Inversion$invertCircle(circ)
circ
a Circle
object
A Circle
object or a Line
object.
# A Pappus chain # https://www.cut-the-knot.org/Curriculum/Geometry/InversionInArbelos.shtml opar <- par(mar = c(0,0,0,0)) plot(0, 0, type = "n", asp = 1, xlim = c(0,6), ylim = c(-4,4), xlab = NA, ylab = NA, axes = FALSE) A <- c(0,0); B <- c(6,0) ABsqr <- c(crossprod(A-B)) iota <- Inversion$new(A, ABsqr) C <- iota$invert(c(8,0)) Sigma1 <- Circle$new((A+B)/2, sqrt(ABsqr)/2) Sigma2 <- Circle$new((A+C)/2, sqrt(c(crossprod(A-C)))/2) draw(Sigma1); draw(Sigma2) circ0 <- Circle$new(c(7,0), 1) iotacirc0 <- iota$invertCircle(circ0) draw(iotacirc0) for(i in 1:6){ circ <- circ0$translate(c(0,2*i)) iotacirc <- iota$invertCircle(circ) draw(iotacirc) circ <- circ0$translate(c(0,-2*i)) iotacirc <- iota$invertCircle(circ) draw(iotacirc) } par(opar)
transformCircle()
An alias of invertCircle
.
Inversion$transformCircle(circ)
circ
a Circle
object
A Circle
object or a Line
object.
invertLine()
Inversion of a line.
Inversion$invertLine(line)
line
a Line
object
A Circle
object or a Line
object.
transformLine()
An alias of invertLine
.
Inversion$transformLine(line)
line
a Line
object
A Circle
object or a Line
object.
invertGcircle()
Inversion of a generalized circle (i.e. a circle or a line).
Inversion$invertGcircle(gcircle)
gcircle
a Circle
object or a Line
object
A Circle
object or a Line
object.
compose()
Compose the reference inversion with another inversion. The result is a Möbius transformation.
Inversion$compose(iota1, left = TRUE)
iota1
an Inversion
object
left
logical, whether to compose at left or at right (i.e.
returns iota1 o iota0
or iota0 o iota1
)
A Mobius
object.
clone()
The objects of this class are cloneable with this method.
Inversion$clone(deep = FALSE)
deep
Whether to make a deep clone.
inversionSwappingTwoCircles
,
inversionFixingTwoCircles
,
inversionFixingThreeCircles
to create some inversions.
## ------------------------------------------------
## Method `Inversion$print`
## ------------------------------------------------
Inversion$new(c(0,0), 2)
## ------------------------------------------------
## Method `Inversion$invertCircle`
## ------------------------------------------------
# A Pappus chain
# https://www.cut-the-knot.org/Curriculum/Geometry/InversionInArbelos.shtml
opar <- par(mar = c(0,0,0,0))
plot(0, 0, type = "n", asp = 1, xlim = c(0,6), ylim = c(-4,4),
xlab = NA, ylab = NA, axes = FALSE)
A <- c(0,0); B <- c(6,0)
ABsqr <- c(crossprod(A-B))
iota <- Inversion$new(A, ABsqr)
C <- iota$invert(c(8,0))
Sigma1 <- Circle$new((A+B)/2, sqrt(ABsqr)/2)
Sigma2 <- Circle$new((A+C)/2, sqrt(c(crossprod(A-C)))/2)
draw(Sigma1); draw(Sigma2)
circ0 <- Circle$new(c(7,0), 1)
iotacirc0 <- iota$invertCircle(circ0)
draw(iotacirc0)
for(i in 1:6){
circ <- circ0$translate(c(0,2*i))
iotacirc <- iota$invertCircle(circ)
draw(iotacirc)
circ <- circ0$translate(c(0,-2*i))
iotacirc <- iota$invertCircle(circ)
draw(iotacirc)
}
par(opar)
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