In Lua itself the backslash is also a escape character inside "...". Replace "..." by [[...]]. With the latter \ is not an escape character any longer:
\documentclass{article}
\usepackage{luacode}
\begin{document}
\begin{luacode*}
i=6
j=8
tex.print([[\begin{tabular}{|l|l|}\hline]])
tex.print(i.."&"..j)
tex.print([[\\ \hline]])
tex.print([[\end{tabular}]])
\end{luacode*}
\end{document}
In my experience, new lines inside double brackets are problematic, so I avoid them.
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
The problem is that there are 3 interpretation stages involved.
luacode*environment)I had forgotten the last stage.. So the solution is:
or