[R] lines and points without margin

Ben Bolker bbolker at gmail.com
Tue Dec 14 16:52:01 CET 2010

Andrew Collier <collierab <at> gmail.com> writes:

> i am sure that this is a trivial question but i have not been able to
> find an answer by searching the mailing lists. i want to plot points on
> a graph, joined by lines. the command that i am using is
> points(x, y, type = "b", pch = 21)
> this plots nice open circles at the data points and draws lines between
> them. however, the lines do not come all the way up to the edge of the
> circles but stop some small distance away so that there is an empty
> "margin" around the circles. is there a way to get rid of this margin?
> my first guess was that there would be an option to par() but i did not
> find anything there. any suggestions would be appreciated.

  Does type="o" do what you want?  (See ?plot )
  However, this actually overplots (which would be OK with filled
point types, or if you don't care if you have lines running across
your open points) -- it doesn't draw the line "up to the edge of
the point".

  It looks like the size of the spacing is hard-coded at a fairly
deep level: in plot.c, within the do_plot_xy function, there is
a spacing factor which seems to be encoded as "half the width of
standard character in the current plotting coordinates".

  Ben Bolker

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