Re: [NTG-context] m-graph read data and plot

13 Aug 2015


      On 8/13/2015 9:37 PM, John Kitzmiller wrote:
...
On Aug 9, 2015, at 8:38 AM, Alan BRASLAU mailto:alan.braslau@cea.fr> wrote:
...
One needs to think about closing the data file as ConTeXt opens a single
MP instance that is run throughout the entire document AND over its
multiple runs. If the file is left open, a second run will try to read
on from the point where it left off.
THIS IS A SUBTLE POINT THAT SHOULD BE NOTICED BY ALL MPLIB USERS!
Thank you for this insight Alan! Two results immediately helpful are:
1) data can be put at the top of the .tex file
2) autogrids can be rendered and then drawn over
The following may not be the best way, but it works to read data from
the top of the .tex file and then plot on the autogrid.
% 1 0.5 2.5
% 2 1 3.5
\usemodule[graph]
\startMPpage[instance=graph,offset=2mm]
   draw begingraph(3cm,5cm);
   numeric a[];
     gdata("read1.tex", v,
       setrange(0,0,3,4);
     );
     closefrom "read1.tex";
autogrid(,grid.lft) withcolor .7white;
gdata("read1.tex",v,
     for j = 1 upto 3:
         a[j] := scantokens v[j];
       endfor;
       path b;
       augment.b(a1,a2);
       augment.b(a1,a3);
       setrange(0,0,3,4);
       gdraw b;
     );
     closefrom "read1.tex";
   endgraph;
\stopMPpage
an apetizer:

\usemodule[graph]

\startluacode
     local d = nil
     function MP.set(data)
         d = data
     end
     function MP.n()
         mp.print(d and #d or 0)
     end
     function MP.get(i,j)
         mp.print(d and d[i] and d[i][j] or 0)
     end
\stopluacode

\startluacode
     MP.set {
         { 1, 0.5, 2.5 },
         { 2, 1.0, 3.5 },
     }
\stopluacode

\startMPpage[instance=graph,offset=2mm]
draw begingraph(3cm,5cm);
     numeric a[];
     for j = 1 upto MP.n() :
         path b;
         augment.b(MP.get(j,1),MP.get(j,2));
         augment.b(MP.get(j,1),MP.get(j,3));
         setrange(0,0,3,4);
         gdraw b;
         endfor ;
endgraph ;
\stopMPpage


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