Create a custom linear transformation

This function lets you compose transformations based on a sequence of linear transformations. If the transformations are parameterised the parameters will become arguments in the transformation function. The transformations are one of rotate, shear, stretch, translate, and reflect.

Usage

linear_trans(...)

rotate(angle)

stretch(x, y)

shear(x, y)

translate(x, y)

reflect(x, y)

Arguments

...

A number of transformation functions.

angle

An angle in radians

x

the transformation magnitude in the x-direction

y

the transformation magnitude in the x-direction

Value

linear_trans creates a trans object. The other functions return a 3x3 transformation matrix.

Examples

trans <- linear_trans(rotate(a), shear(1, 0), translate(x1, y1))
square <- data.frame(x = c(0, 0, 1, 1), y = c(0, 1, 1, 0))
square2 <- trans$transform(square$x, square$y, a = pi / 3, x1 = 4, y1 = 8)
square3 <- trans$transform(square$x, square$y, a = pi / 1.5, x1 = 2, y1 = -6)
square <- rbind(square, square2, square3)
square$group <- rep(1:3, each = 4)
ggplot(square, aes(x, y, group = group)) +
  geom_polygon(aes(fill = factor(group)), colour = 'black')