Shifts points by (dx, dy).
Details
trans objects compose with +, applied left to right: t1 + t2 means
"apply t1's effect first, then t2's". For example,
trans_translate(1, 0) + trans_rotate(pi / 2) translates a point one
unit right, then rotates the result a quarter turn about the origin –
not the same as trans_rotate(pi / 2) + trans_translate(1, 0), which
rotates first and translates second. Internally, (t1 + t2)@matrix is
t2@matrix %*% t1@matrix, since points are homogeneous column vectors
transformed as matrix %*% point.
See also
Other transform helpers:
trans(),
trans_affine(),
trans_chain(),
trans_fn(),
trans_identity(),
trans_reflect(),
trans_rotate(),
trans_scale(),
trans_shear(),
trans_warp()
Examples
draw(shape_square(side = 1, trans = trans_translate(2, 0)))
# overlay the original (faded) with the translated copy (solid)
original <- shape_rectangle(
width = 1.5,
height = 0.6,
fill_alpha = 0.3,
color_alpha = 0.3
)
draw(sketch() + original + (original + trans_translate(1, 0.5)))
# composition order matters: translate-then-rotate differs from
# rotate-then-translate -- a fixed xlim/ylim makes the difference in
# final position visible (a lone shape otherwise always fills its own
# auto-scaled frame)
square <- shape_square(x = 1, side = 0.4)
draw(
square + trans_translate(1, 0) + trans_rotate(pi / 2),
xlim = c(-1, 3),
ylim = c(-1, 3)
)
draw(
square + trans_rotate(pi / 2) + trans_translate(1, 0),
xlim = c(-1, 3),
ylim = c(-1, 3)
)
