[Tex/LaTex] How to use mplib directly from lua

graphicsluatexmetapost

I am trying to plot some graphics calling mplib from lualatex.
The 'standard' way is the use of luamplib package and mplibcode environment. I was wandering, is there a way to call mplib from lua directly? As long as mplibcode is just an 'easy' and 'LaTeX' way to do so, it should be possible. However, I could not find any documentation or examples on this topic. Unfortunately, the explanations in the luamplib manual stops at line 54, before I am really able to get an idea of the machinery behind it. It seems that there are few people who knows how to do this, they just had no time to provide others with any documentation.

This thread proposes the solution which seems unnatural: there is lua code which generates tex code inside Tikz environment which is then in turn calls mplib via lua.

Example

The minimal example is:

example.tex:

\documentclass{article}
\usepackage{luamplib}

\begin{document}
\directlua{ dofile('testmplibmin.lua') }
\directlua{ StartMP() }

\end{document}

testmplibmin.lua:

local mpkpse = kpse.new("luatex", "mpost")

local function finder(name, mode, ftype)
  if mode == "w" then
    return name
  else
  return mpkpse:find_file(name,ftype)
  end
end

function StartMP()
  local mplib = require('mplib')
  local mpx=mplib.new({find_file=finder,ini_version=true})
  local result = mpx:execute('input plain;')
  result=mpx:execute('beginfig(1); draw fullcircle scaled 20 withcolor red; endfig;')
  local t,e,l = result.term,result.error,result.log
  if result.status>0 then
    tex.print([[Result of mplib execute is unsuccessfull.]])
  else
    if result.fig then
      tex.sprint('Converted something: \\vrule\\vbox{\\hrule')
      local converted=luamplib.convert(result)
      tex.sprint('\\hrule}\\vrule')
    else
      tex.print([[No figure output.]])
      tex.print([[Log:]])
      tex.print(l)
    end
  end
  mpx:finish()
end

I will try to improve (=shorten) it more. E.g., I believe that there is a way to use finder function from luamplib. Any comments are welcome.

Best Answer

The file mplibapi.pdf from the metapost source distrobution documents the low-level interface. Still, it is probably wise to read the luamplib code as well, because the conversion from mplib's return table (containing images) to PDF literal code is not quite trivial. http://www.tug.org/metapost/src/manual/mplibapi.pdf

Related Solutions

[Tex/LaTex] Ploting a function using mplib in lualatex

This is how I would do it in ConTeXt. I don't know if similar functionality is available in a LaTeX package. Basically, I do the calculations in lua and write the result inside a \startMPcode .. \stopMPcode environment.

\startluacode
  require("math")
  local sin = math.sin
  local cos = math.cos 
  local pi  = math.pi 

  local function scale(x) 
    return x .. " * 1cm"
  end
  local function pair(x,y) 
    return "(" .. scale(x) .. "," .. scale(y) .. ")"
  end

  local function point(f,x)
    return pair(x, f(x))
  end

  userdata = userdata or {}

  function userdata.draw_function(f, a, b, n) 
    local step = (b-a)/n
    local path = {}
    local i = 0 
    for x = a, b, step do 
      path[i] = point(f,x) 
      i = i + 1
    end  
    path = table.concat(path, "--")

    context("draw " .. path .. " withpen pencircle scaled 2bp;")
  end

  function userdata.draw_x_axis(from, to)
      context(" drawarrow " .. pair(from,0) .. " -- " .. pair(to,0) .. "; ")
      context(" label.rt ( btex $x$ etex , " .. pair(to,0) .. ") ;")
  end

  function userdata.draw_y_axis(from, to)
      context(" drawarrow " .. pair(0, from) .. " -- " .. pair(0,to) .. "; ")
      context(" label.top ( btex $y$ etex , " .. pair (0,to) .. ") ;")
  end

  function userdata.plot()

    userdata.draw_x_axis(-2, 6.5) 
    userdata.draw_y_axis(-2.2, 2.2)


    local f = function (x) 
      return sin(2*x) + cos(x)
    end

    userdata.draw_function(f, 0, 2*pi, 40)
  end

\stopluacode

\starttext
  \ctxlua
    {context.startMPcode() ;
      userdata.plot() ;
     context.stopMPcode() ; }
\stoptext

However, this assumes that everything that is written inside teh userdata.plot() function is MP code. If you also want that function to print stuff to the TeX stream, then you can store all the MP code inside a \startMPdrawing and \stopMPdrawing environment and retrieve them using \getMPdrawing.

\startluacode
  require("math")
  local sin = math.sin
  local cos = math.cos 
  local pi  = math.pi 

  local function scale(x) 
    return x .. " * 1cm"
  end
  local function pair(x,y) 
    return "(" .. scale(x) .. "," .. scale(y) .. ")"
  end

  local function point(f,x)
    return pair(x, f(x))
  end

  userdata = userdata or {}

  function userdata.draw_function(f, a, b, n) 
    local step = (b-a)/n
    local path = {}
    local i = 0 
    for x = a, b, step do 
      path[i] = point(f,x) 
      i = i + 1
    end  
    path = table.concat(path, "--")

  context.startMPdrawing()
    context("draw " .. path .. " withpen pencircle scaled 2bp;")
  context.stopMPdrawing()
  end

  function userdata.draw_x_axis(from, to)
    context.startMPdrawing()
      context(" drawarrow " .. pair(from,0) .. " -- " .. pair(to,0) .. "; ")
      context(" label.rt ( btex $x$ etex , " .. pair(to,0) .. ") ;")
    context.stopMPdrawing()
  end

  function userdata.draw_y_axis(from, to)
    context.startMPdrawing()
      context(" drawarrow " .. pair(0, from) .. " -- " .. pair(0,to) .. "; ")
      context(" label.top ( btex $y$ etex , " .. pair (0,to) .. ") ;")
    context.stopMPdrawing()
  end

  function userdata.plot()
    userdata.draw_x_axis(-2, 6.5) 
    userdata.draw_y_axis(-2.2, 2.2)


    local f = function (x) 
      return sin(2*x) + cos(x)
    end

    userdata.draw_function(f, 0, 2*pi, 40)
  end

\stopluacode

\starttext
  \ctxlua
    { context.resetMPdrawing() ;
      userdata.plot() ;
      context.MPdrawingdonetrue() ;
      context.getMPdrawing() ; }
\stoptext

[Tex/LaTex] How to use lua code from external file in lualatex

The best way to do this is to make your external file into a module. That means, you make sure that all variables are local and in the end you return a table which exports all user-accessible functions. For example f(x,y,z) is not going to be used outside, so I won't export it. As you can see I can also export functions under a different name.

-- Differential equation of the Lorenz attractor
local function f(x,y,z)
    local sigma = 3
    local rho = 26.5
    local beta = 1
    return {sigma*(y-x), -x*z + rho*x - y, x*y - beta*z}
end

-- Code to write PGFplots data as coordinates
local function print_LorAttrWithEulerMethod(h,npoints,option)
    -- The initial point (x0,y0,z0)
    local x0 = 0.0
    local y0 = 1.0
    local z0 = 0.0
    -- we add a random number between -0.25 and 0.25
    local x = x0 + (math.random()-0.5)/2
    local y = y0 + (math.random()-0.5)/2
    local z = z0 + (math.random()-0.5)/2
    if option~=[[]] then
        tex.sprint("\\addplot3["..option.."] coordinates{")
    else
        tex.sprint("\\addplot3 coordinates{")
    end
    -- we dismiss the first 100 points to go into the attractor
    for i=1, 100 do
        local m = f(x,y,z)
        x = x + h * m[1]
        y = y + h * m[2]
        z = z + h * m[3]
    end
    for i=1, npoints do
        local m = f(x,y,z)
        x = x + h * m[1]
        y = y + h * m[2]
        z = z + h * m[3]
        tex.sprint("("..x..","..y..","..z..")")
    end
    tex.sprint("}")
end

return { LorenzAttractor = print_LorAttrWithEulerMethod }

An advantage of having the Lua code in a separate file is that you do not have to worry about catcodes. Therefore you don't need the luacode package at all. The module you created in scrap.lua can be loaded like any regular Lua module. Usually you would load it like

local scrap = require("scrap")

but that won't work in LuaTeX because the scrap variable would only be local to the \directlua chunk it is mentioned in and can hence not be used in other chunks. Therefore you have to make a global variable scrap to encapsulate the module

\directlua{scrap = require("scrap")}

The full document would read

\documentclass{article}
\usepackage{pgfplots}
\usepackage{tikz}

\directlua{scrap = require("scrap")}

\newcommand\addLUADEDplot[3][]{%
\directlua{scrap.LorenzAttractor(#2,#3,[[#1]])}%
}

\begin{document}

\begin{tikzpicture}
\begin{axis}
% SYNTAX: Solution of the Lorenz system
% with step h=0.02 sampled at 1000 points.
\addLUADEDplot[color=red,smooth]{0.02}{1000};
\addLUADEDplot[color=green,smooth]{0.02}{1000};
\addLUADEDplot[color=blue,smooth]{0.02}{1000};
\addLUADEDplot[color=cyan,smooth]{0.02}{1000};
\addLUADEDplot[color=magenta,smooth]{0.02}{1000};
\addLUADEDplot[color=yellow,smooth]{0.02}{1000};
\end{axis}
\end{tikzpicture}

\end{document}

Example

Best Answer

Related Solutions

[Tex/LaTex] Ploting a function using mplib in lualatex

[Tex/LaTex] How to use lua code from external file in lualatex

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