Dear R users,
The following issue has been already documented, but, if I am not
mistaken, not yet solved.
This issue appears while trying to plot arrows with "geom_segment"
(package ggplot2), with polar coordinates ("coord_polar"). The
direction
of some arrows is wrong (red rectangle). Please find herewith an example.
Does someone know how to deal with that issue?
Best Regards,
Pascal Oettli
#----------------------------------------------------------------------------------
# Example adapted from the help page of "geom_segment"
library(ggplot2)
library(grid)
d <- data.frame(x1=-135.3, x2=-158.3, y1=37.2, y2=45.2)
p <- ggplot(seals, aes(x = long, y = lat))
p1 <-
ggplot() +
coord_cartesian() +
geom_rect(data=d, mapping=aes(xmin=x1, xmax=x2, ymin=y1, ymax=y2),
fill="red", color="red", alpha=0.5) +
geom_segment(data=seals, aes(x = long, y = lat, xend = long +
delta_long, yend = lat + delta_lat), arrow = arrow(length =
unit(0.2,"cm")))
p2 <-
ggplot() +
coord_polar() +
geom_rect(data=d, mapping=aes(xmin=x1, xmax=x2, ymin=y1, ymax=y2),
fill="red", color="red", alpha=0.5) +
geom_segment(data=seals, aes(x = long, y = lat, xend = long +
delta_long, yend = lat + delta_lat), arrow = arrow(length =
unit(0.2,"cm")))
grid.newpage()
pushViewport(viewport(layout = grid.layout(3, 2, heights = unit(c(0.5,
0.5, 5), "null"))))
grid.text("Example taken from '?geom_segment'", vp =
viewport(layout.pos.row = 1, layout.pos.col = 1:2))
grid.text("Cartesian coordinates", vp = viewport(layout.pos.row = 2,
layout.pos.col = 1))
grid.text("Polar coordinates", vp = viewport(layout.pos.row = 2,
layout.pos.col = 2))
print(p1, vp = viewport(layout.pos.row = 3, layout.pos.col = 1))
print(p2, vp = viewport(layout.pos.row = 3, layout.pos.col = 2))
