[Rd] documenation for arrows() is backwards (PR#7839)

[hoffman.mm+R-project.org at ebi.ac.uk]

Full_Name: Michael Hoffman
Version: 2.1.0
OS: Linux (Fedora Core 3, kernel 2.6.11-1.14_FC3)
Submission from: (NULL) (193.62.199.8)


help(arrows) says:

"""
     arrows(x0, y0, x1, y1, length = 0.25, angle = 30, code = 2,
            col = par("fg"), lty = NULL, lwd = par("lwd"), xpd = NULL)

...

     If 'code=2' an arrowhead is drawn at '(x0[i],y0[i])' and if
     'code=1' an arrowhead is drawn at '(x1[i],y1[i])'.  If 'code=3' a
     head is drawn at both ends of the arrow.  Unless 'length = 0',
     when no head is drawn.
"""

If you do:

plot(c(-1, 1), c(-1, 1), col=0)
arrows(x0=0, y0=0, x1=0, y1=1, code=2)

it is pretty clear that the arrowhead is drawn at x1, y1 with code=2. If you
switch to code=1, the arrowhead is drawn at x0, y0. Either the documentation or
the function is incorrect.