[EMAIL PROTECTED] writes:
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.
One way to decide is to compare with Splus. Now that doesn't have a
'code' argument and the arguments are named x1,y1,x2,y2 (I wonder why
R wanted to be different here?), but they do put the arrowheads at the
*to* end, which does seem to be the sensible thing to do.
Arguably, using 'code=2' as the default is a bit weird,
An argument for the current encoding is that it encodes arrowhead end in the bits of code: 00 = no arrowhead, 01 = arrowhead at origin, 10 = arrowhead at destination, 11 = arrowhead at both.
> but changing > it could be quite painful. I.e., we should fix the docs.
Yes, definitely.
BTW, the docs also might say that code=0 makes arrows behave like
segments(). It is also a bit strange that the code argument isn't
vectorized, which might have been useful.
Yes, that would be a reasonable change.
Duncan
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