When drawing with TikZ, I find sometime convenient to use polar coordinates (angle:distance), as in this MWE


   [pole/.style={circle,draw=gray,fill=gray,thick,text width=2cm, align=center}]
  \node[pole] (eur) at (60:3cm) {Europe};
  \node[pole] (afr) at (300:3cm) {Afrique};
  \node[pole] (amq) at (180:3cm)  {Amérique};

How can I get a similar effect using METAPOST ? I could'nt find direct answer in the manual. I am quite sure one can achieve the same with a good knowledge of geometry. It would be good for scripting.

So far, my METAPOST equivalent would be

u:=1cm ;
label(btex Amérique etex, (-3u,0) ) ;
label(btex Europe etex, (u,2u) ) ;
label(btex Afrique etex, (u,-2u) ) ;
endfig ;

Of course this are not polar coordinates and I am even not sure angles are the same as in TikZ. Since I am not a scientist, I would be glad to have some explanation if some geometry knowledge is required.

  • You can easily convert r and φ to cartesian coordinates using the prescription (x,y) = (r*cos(φ),r*sin(φ)) Nov 15 '18 at 20:21

Use the dir operator. From the MetaPost manual:

enter image description here

Here with MetaFun in ConTeXt:

u:=1cm ;
label(btex Amérique etex, 3u*dir 60) ;
label(btex Europe etex, 3u*dir 300) ;
label(btex Afrique etex, 3u*dir 180) ;
  • Thanks. I wouldn't have been able to find this on my own. It's been too long since I learnt what does cos and sin reflect… But now I see the point.
    – sztruks
    Nov 15 '18 at 21:24
  • There is also an operator angle that does the opposite, so that angle dir 60 should return 60. A bit like atan2 in other languages.
    – Thruston
    Nov 15 '18 at 21:42
  • As a matter of style you could also write 3 dir 60 scaled u.
    – Thruston
    Nov 15 '18 at 21:47
  • @Thruston angle does exactly perform atan2 (at least in double and decimal mode) github.com/TeX-Live/texlive-source/blob/… Nov 15 '18 at 21:50
  • 1
    Yes quite right. In my old-fashioned British way, when I say “a bit like” I mean “exactly the same as”…
    – Thruston
    Nov 15 '18 at 21:55

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