Errors Mpgraph in ConTeXt

Question

I need to put some bar charts in a ConTeXt document. I'm using mkiv from TeX Live 2011, under Gentoo GNU/Linux. I tried using Gnuplot but I found mpgraph suits better my needs.

I'm using this TeX file

\usemodule[graph]
\usemodule[sarith]

\enableregime[utf-8]
\starttext

\startMPcode
beginfig(1)
  draw begingraph(12cm,6cm);
    glabel.lft(btex Eje Y etex, OUT);
    glabel.bot(btex Eje X etex, OUT);
    gdata("data.d",
        $,
        path p;
        augment.p (0,$1);
        augment.p ($2,$1);
        augment p ($2,$1 Sadd "1");
        augment p (0,$1 Sadd "1");
        gdraw p withpen pencircle scaled 2bp withcolor red;
    );
  autogrid(grid.bot,grid.lft) withcolor .85white;
  endgraph;
endfig;
\stopMPcode
\stoptext

and this data file

1 4
2 2
3 1
4 2
5 4

as a minimal 'working' example.

However, some strange is happening: I can't use any operator from sarith module (used in mpgraph module for drawing boxes). I got this output with ConTeXt. I tried compiling with Metapost, although I got no errors or warnings the output .dvi is corrupted.

I've tried also with TeX Live 2012 under Windows 7. I can't compile there because of the sarith thing, but when I comment that lines it works. But doing the same thing in my Gentoo box works, excepting that text for labels or axis doesn't appear, just a very little square. I don't understand what is happening, even the example from the ConTeXt wiki doesn't work. Clues? Any help is very appreciated!

Answer 1

You need to replace \usepackage[sarith] with

\startMPinitializations
input sarith;
\stopMPinitializations

sarith is not a ConTeXt module, rather it is a metapost package, so needs to be included at the metapost end.

Moreover, as morbusg pointed out, there is no need to add beginfig(1)...endfig in a MPcode environment. With these two changes, the following works:

\usemodule[graph]
\startMPinitializations
input sarith;
\stopMPinitializations

\starttext

\startMPcode
  draw begingraph(12cm,6cm);
    glabel.lft(btex Eje Y etex, OUT);
    glabel.bot(btex Eje X etex, OUT);
    gdata("data.d",
        $,
        path p;
        augment.p (0,$1);
        augment.p ($2,$1);
        augment p ($2,$1 Sadd "1");
        augment p (0,$1 Sadd "1");
        gdraw p withpen pencircle scaled 2bp withcolor red;
    );
  autogrid(grid.bot,grid.lft) withcolor .85white;
  endgraph;
\stopMPcode
\stoptext

Answer 2

To change the font for the numbers on the grids I discovered that if I manually set the grid values, instead of using the automatic set, the font is converted to the document format. Here is an example from John Handy's MPGraph documentation with my revision:

Original

draw begingraph(6.5cm,4.5cm);
    setrange(80,0, 90,whatever);
        glabel.bot(btex Year etex, OUT);
        glabel.lft(btex \vbox{\hbox{Emissions in} \hbox{thousands of}
            \hbox{metric tons} \hbox{(heavy line)}}etex, OUT);
        gdraw "lead.d" withpen pencircle scaled 1.5pt;
        autogrid(,otick.lft);
        setcoords(linear,linear);
    setrange(80,0, 90,whatever);
        glabel.rt(btex \vbox{\hbox{Micrograms} \hbox{per cubic}
            \hbox{meter of air} \hbox{(thin line)}}etex, OUT);
    gdraw "lead.d";
        autogrid(otick.bot,otick.rt);
endgraph;

with

draw begingraph(6.5cm,4.5cm);
    setrange(79.5,0, 90.5,80) ;
    glabel.bot(btex Year etex, OUT) shifted(-8pt,-2pt);
    glabel.lft(btex \vbox{% -- \hss fills space horizontally; \strut fixes line space
        \hbox to 5cm {\hss \strut Emissions in thousands of \hss}
        \hbox to 5cm {\hss \strut metric tons (solid line) \hss}
    }
    etex, OUT) shifted(83pt,17pt) rotated 90;
    gdraw "lead.d" withpen pencircle scaled 1pt;
    itick.lft(format("\%2",0),0) withcolor white;
    itick.lft(format("\%2",20),20) withcolor white;
    itick.lft(format("\%2",40),40) withcolor white;
    itick.lft(format("\%2",60),60) withcolor white;
    itick.lft(format("\%2",80),80) withcolor white;
    frame.lft withcolor white ;

    otick.bot(format("\%2",80),80) withcolor white;
    otick.bot(format("\%2",82),82) withcolor white;
    otick.bot(format("\%2",84),84) withcolor white;
    otick.bot(format("\%2",86),86) withcolor white;
    otick.bot(format("\%2",88),88) withcolor white;
    otick.bot(format("\%2",90),90) withcolor white;
endgraph;

Try this out.