GMT5 How to draw a double-headed straight line?

Hi.
I am struggling to draw a double-headed arrow with psxy. I cannot figure 
out what the documentation says to do. Can someone suggest how that 
might be done?

I can make a curved single-headed line using an example in the doc.

J

-- 
John Helly, University of California, San Diego / San Diego Supercomputer Center / Scripps Institution of Oceanography / 760 840 8660 mobile / stonesteps (Skype) / stonesteps7 (iChat) / http://www.sdsc.edu/~hellyj


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