[R] in axis() suppressing axis line but keeping tick marks

[Peter Dalgaard]

Andrew Yee wrote:
> I've been trying to figure out a parameter that will let you separately
> adjust the parameters for the axis line from the tick mark.
>
> In the following example, I would like to suppress the axis line, but keep
> the tick marks.
>   
The source code is the ultimate reference. We have in do_axis in 
src/main/plot.c:

    if (doticks) {
        gpptr(dd)->col = col;/*was fg */
        GLine(axis_low, axis_base, axis_high, axis_base, NFC, dd);
        for (i = 0; i < n; i++) {
            x = REAL(at)[i];
            if (low <= x && x <= high) {
                x = GConvertX(x, USER, NFC, dd);
                GLine(x, axis_base, x, axis_tick, NFC, dd);
            }
        }
    }

and, as you see, there is no way the line parameters can change between 
the GLine calls, no hope of finding a magical par() setting. So I'm 
afraid you have to bite the bullet, do the relevant coordinate 
calculations, and use segments() do draw the ticks. (Or try convincing 
Paul Murrell to change the design, but that takes longer...).

-- 
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