[pstricks] psarc

Herbert Voss Herbert.Voss at FU-Berlin.DE
Sat Nov 22 16:05:14 CET 2008

Poul Riis schrieb:
> Still one problem remains in my figure below: How can I reverse the
> direction of the arrow in case w0y is positive?

that is difficult.
An easy way is to use another (short) \psparabola bow
for the arc with an arrow. E.g.

  (!x0 0.2 add zT 1 sub)(!xT x0 add zT 3 add)%

the lines are too long, but you'll find better values.
Another, but more difficult solution is to draw the arc
completely inside PostScript. E.g.

  \code{ xT x0 add 5.69 mul /x ED zT 5.60 mul /y ED 1.5 5.69 mul /r ED
         w0y 0 gt
           { x r sub dup y exch 1 add y 1 add 4 2 roll ArrowA pop pop
           { x r add dup y exch 1 sub y 1 add 4 2 roll ArrowB pop pop
pop pop stroke}
         x y r 90 w0y abs wang mul sub 90 w0y abs wang mul add arc }

look into the documentation for \code and \arrows.


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