On 12-12-2011 23:13, Mojca Miklavec wrote:

Either way the moral of the story is still the same: context parsing is very very very confusing and you don't want to go there. In particular you never know if something should be parsed and executed before or after gnuplot processing.

Actually this kind of parsing is rather predictable: you use a buffer, so no parsing takes place. On the other hand, the mp environments are passed directly and therefore the content is expanded, unless a macro is defined as unexpandable (which many macros are). Hans ----------------------------------------------------------------- Hans Hagen | PRAGMA ADE Ridderstraat 27 | 8061 GH Hasselt | The Netherlands tel: 038 477 53 69 | voip: 087 875 68 74 | www.pragma-ade.com | www.pragma-pod.nl -----------------------------------------------------------------

Am Montag, den 12.12.2011, 23:07 +0100 schrieb Mojca Miklavec:

On Mon, Dec 12, 2011 at 22:39, Paul Menzel wrote:

...

I have two coefficients saved in a text file

-0.157737135681261 -0.211443105668896

and I want to use them to plot a line with gnuplot.

Having several of those files I want to use Lua to create the formula for the line for me.

I have not yet figured out how to read values from a file in Lua and just tried to print a constant to the gnuplot command.

I tried the following.

\usemodule[gnuplot]

\startGNUPLOTscript[lua] plot \ctxlua{context(1.2 * x + 3)} \stopGNUPLOTscript

This won't work. The reason is that contents between \startGNUPLOTscript and \stopGNUPLOTscript are not parsed by ConTeXt on purpose.

It was very very very painful if not impossible to get it right with parsing. I often do things like \def\E#1{$10^{#1}$}

\startGNUPLOTscript[name] set logscale y set format y "\\E{%T}" plot sin(x) t '$\sin(x) [\E{3}]$' # usually something else with logscale, but just to show the point \stopGNUPLOTscript

and if ConTeXt starts parsing this it becomes a pure nightmare. Realize that it can easily happen that ConTeXt then writes out set logscale y set format y " E plot sin(x) t '\math{\mathrm{sin}(x) [{10^{3}}]}'

However, \startGNUPLOTinclusions is parsed and you could in theory misuse that, but it would be very bad coding practice.

Thank you very much for your explanations.

It would be a lot better to come up with some proposal how to change the interface to enable what you want to do. (To be honest, it is still on my todo list to migrate to Aditya's filter module in the background, but I don't find the courage to start since I have no idea how many bugs will creep in.)

I do not know this very well, so I do not know what would change when using the filter module. I guess in the end being able to pass a plt-file to `\startGNUPLOTscript` would be enough.

But a serious question: what *exactly* do you want to do with lua that you are unable to do with some (even though ugly) gnuplot trickery?

I do not know. This was just a product out of my ignorance. Searching for `gnuplot load parameters` or something like that only turned `fit` related stuff. Thinking about this, I should have searched harder or looked at the manual or examples.

Gnuplot does have some basic programmable capabilities. I can imagine that you should be able to do something like:

# params.dat a=-0.157737135681261 b=-0.211443105668896

\startGNUPLOTinclusions f(x,a,b)=a*x+b \stopGNUPLOTinclusions

\startGNUPLOTscript[name] load 'params.dat' plot f(x,a,b) \stopGNUPLOTscript

And if needed you can create params.dat on the fly (but I believe that the same should be doable even if you start with just pure data values and do some dirty tricks in gnuplot).

That pretty much what I need. Thank you! What I do is to do simulations and then do the linear regression using R [1]. (I know gnuplot can do that too, but I got some errors with it and using R seems easier for me.) Then the calculated coefficient are saved to a separate file because having discovered your nice gnuplot module I want to use that for plotting. Now I need to read in those parameters. I guess I have to compose the plot manually but those parameters were essential.

Yet another trick could be to create a text file on the fly with lua (if you really really really need that) and then your script only says something like.

# bla.plt created on the fly with lua scripts plot 1.2 * x + 3

\startGNUPLOTscript[bla] load 'bla.plt' \stopGNUPLOTscript

I leave creating a suitable 'bla.plt' with lua to others ...

That is in my opinion the best solution. If I want to script something there are enough solutions already. Being able to use the tools of once choice and to insert the result should fit everyone’s need. Thank you again very much for your help. Thanks, Paul [1] http://www.r-project.org/

On Mon, 12 Dec 2011, Mojca Miklavec wrote:

It would be a lot better to come up with some proposal how to change the interface to enable what you want to do. (To be honest, it is still on my todo list to migrate to Aditya's filter module in the background, but I don't find the courage to start since I have no idea how many bugs will creep in.)

Hey, there are no bugs in the filter module ;) If you can send me a complete behavioral description of what the gnuplot module does (what should be written to gnuplot file, what exact command should be called, etc), then I could easily write a wrapper based on the filter module. But the filter module will not help with the OP's question, as the content I treat the filter environment as a buffer and don't parse it at all. Aditya

On Mon, Dec 12, 2011 at 23:17, Hans Hagen wrote:

You have to twist your mide a bit:

\startluacode  local x = 10  context.startGNUPLOTscript{ "lua" }  context("plot %s",1.2 * x + 3)  context.stopGNUPLOTscript() \stopluacode

\starttext \useGNUPLOTgraphic[lua] \stoptext

Oh, I like this one! Not that it works at the moment, but fixing the module to make it work is doable (which is not to say that I know how to do it). Mojca