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}
Best Answer
With package
luatextrayou have already loaded packageluacode. This package provides help with the dealing of special characters, see its documentation. In this case\luaexectogether with\%helps. Inside\luaexec\%is a macro that expands to a harmless percent character. Remember,%is usually the comment character in TeX.Answer to the comment with
\%in\directlua:I expect that using
\%within\directluawill not work any longer with the new LuTeX 0.74 with Lua 5.2. Taco Hoekwater (author of LuaTeX) wrote in the luatex mailing list in January 2013 with subject "About lua 5.2 changes":With the standard definition of
\%in LaTeX (\chardef), the string would get the percent character with preceding backslash. In Lua 5.1 the backslash would be ignored. However in Lua 5.2 the percent character would be "anything else" causing an error now.