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Maxima Source Code Blocks in Org Mode

Org Mode support for Maxima

Introduction

Maxima is a computer algebra system descended from Macsyma, which was originally released in 1982. It is released under the terms of the GNU General Public License.

Maxima is written in Common Lisp. It can be accessed and extended in Lisp.

Requirements and Setup

Maxima binaries are available for Windows and Linux. These either require a compatible Common Lisp or an executable Lisp image. Mac OS X users can install via brew or MacPorts. The combinations of operating system and Lisp implementation known to run Maxima can be found on the Maxima ports page.

There are several versions of Maxima, some with different names. The variable org-babel-maxima-command can be set to the name of your Maxima executable. The default value is "maxima".

Maxima ships with Emacs modes. Instructions for configuring them can be found on emacswiki. imaxima is an Emacs front end with image that displays fully typeset math in your Emacs window.

You must activate Maxima by adding a line to org-babel-load-languages: 

(org-babel-do-load-languages
 'org-babel-load-languages
 '((maxima . t))) ; this line activates maxima

Org Mode Features for Maxima Source Code Blocks

Header Arguments

There are no Maxima-specific default header arguments.

There are two Maxima-specific header arguments:

:batch
This can be set to one of Maxima's source-code loaders: batch, load or batchload. The default loader is batchload.
:graphics-pkg
This can set to one of Maxima's graphics packages: draw or plot. The default package is plot.

If a :file filename.ext header argument is provided to a Maxima source block, in conjunction with a :results graphics file header argument, then the graphics device is determined from the file-ending ext. For the plot package, the following graphics devices (gnuplot terminals) are supported: 

png, pdf, ps, svg.

The draw package supports these graphics devices: 

png, jpg, gif, eps, svg, pdf.

The header argument, :cmdline, can be used to pass command line arguments to Maxima.

Sessions

Org-mode support for Maxima does not include sessions.

Result Types

Maxima produces the full range of result types.

Examples of Use

Calculator

The following source code block uses maxima as a calculator for powers of 12, where the powers are passed with a variable. 

#+name: test-maxima
#+header: :exports results
#+header: :var x=1.3121254
#+begin_src maxima
  programmode: false;
  print(12^x);
#+end_src

HTML export of the result: 

26.06280316745402

Solver

Of course, maxima is more than a calculator. 

#+name: solve-maxima
#+header: :exports results
#+begin_src maxima :results output
  programmode: false;
  eq: x**2-16 = 0;
  solution: solve(eq, x);
  print(solution);
#+end_src

HTML export of the result: 

solve: solution:
                                    x = - 4
                                     x = 4
[%t1, %t2]

3D plots

With gnuplot installed (4.0 or higher), 3D graphics are possible. This example is from a tutorial on the maxima/gnuplot interface. 

#+name: 3d-maxima
#+header: :file images/maxima-3d.png
#+header: :exports results
#+header: :results file graphics
#+begin_src maxima
  programmode: false;
  plot3d(atan(-x^2+y^3/4),[x,-4,4],[y,-4,4],[grid,50,50],[gnuplot_pm3d,true]);
#+end_src

HTML export of the Maxima code block result:

maxima-3d.png

Inline Display of Maxima LaTeX Output

Maxima code can be evaluated and displayed inline in Org mode through babel 1 as in the example below, based on RS initial example. 

#+NAME: tex-maxima
#+HEADER: :exports results
#+BEGIN_SRC maxima :results raw
  tex(exp(-x)/x);
#+END_SRC

HTML export of the result:

\[{{e^ {- x }}\over{x}}\]

The :batch header argument

Setting the :batch header argument to batch:

  • allows the use of the :lisp reader;
  • provides a more verbose output;
  • allows one to typeset calculations in LaTeX.

An example with the :lisp reader

Sample code block: 

#+NAME: batch-maxima
#+HEADER: :batch batch
#+HEADER: :exports results
#+HEADER: :results raw
#+HEADER: :wrap example
#+BEGIN_SRC maxima
  (assume(z>0), integrate(t^z*exp(-t),t,0,inf));
  :lisp $%
#+END_SRC

The first line of input computes the integral \(\int_0^{\infty} t^z\,e^{-t}\,dt\), assuming that \(z\) is positive. The second input line uses the :lisp reader to print the internal representation of that result as a sexp.

HTML export of results: 

(assume(z > 0),integrate(t^z*exp(-t),t,0,inf))
                                 gamma(z + 1)
((%GAMMA SIMP) ((MPLUS SIMP) 1 $Z))

An example with line numbering

By default, the command-line option --very-quiet is passed to the Maxima executable; this option suppresses the output of the start-up banner and input/output labels. That can be modified by setting :cmdline --quiet, which allows printing of input/output labels.

Sample code block: 

#+NAME: batch-quiet-maxima
#+HEADER: :batch batch
#+HEADER: :exports results
#+HEADER: :results raw
#+HEADER: :wrap example
#+HEADER: :cmdline --quiet
#+BEGIN_SRC maxima
  rat(1/(x+1) + x/(x-1));
#+END_SRC

HTML export of results: 

(%i1) rat(1/(x+1)+x/(x-1))
                                  2
                                 x  + 2 x - 1
(%o1)/R/                         ------------
                                     2
                                    x  - 1

Maxima's default is to print input in linear (or 1d) fashion, while output is printed in 2d.

LaTeX output

To produce LaTeX output for an extended computation, one needs to set-up a LaTeX printer. This example uses the alt-display package to do that. To print output as LaTeX, Maxima's 2d printer is replaced with org_tex_display; to ensure input lines are not echoed, its 1d printer is replaced with a sink, org_no_display (see also this Note).

Tangle this code block (C-u C-c C-v t): 

#+NAME: maxima-initialize.lisp
#+HEADER: :tangle ./maxima-initialize.lisp
#+HEADER: :exports none
#+HEADER: :eval none
#+begin_src maxima
#$(load("alt-display.mac"),
define_alt_display(org_no_display(output_form), ""),
define_alt_display(org_tex_display(output_form),
  block([],
  printf(true,"~&#+begin_example~%(~a~d)~%",outchar,linenum),
  printf(true,"~&#+end_example~%"),
  tex(second(output_form)))),
set_alt_display(2,org_tex_display),
set_alt_display(1,org_no_display));#$
#+end_src

Next, write a Maxima code block that sets the :cmdline header to read in the initialization code that was just tangled. 

#+NAME: batch-latex-maxima
#+HEADER: :batch batch
#+HEADER: :exports results
#+HEADER: :results raw
#+HEADER: :wrap maximablock
#+HEADER: :cmdline --quiet --preload-lisp ./maxima-initialize.lisp
#+BEGIN_SRC maxima
  (assume(z>0), 'integrate(t^z*exp(-t),t,0,inf) = integrate(t^z*exp(-t),t,0,inf));
  diff(%,z);
#+END_SRC

HTML export of the results: 

(%o1)

\[\int_{0}^{\infty }{t^{z}\,e^ {- t }\;dt}=\Gamma\left(z+1\right)\] 

(%o2)

\[\int_{0}^{\infty }{t^{z}\,e^ {- t }\,\log t\;dt}=\psi_{0}(z+1)\, \Gamma\left(z+1\right)\]

Note

Prior to version 5.47, Maxima could only pre-load a lisp file; to get around this constraint, the Maxima code is written into a lisp file, and the #$ reader macro is used to read the Maxima code. In versions 5.47 and higher, the Maxima code can be put in a .mac file and pre-loaded without the need for such tricks.

The :graphics-pkg header argument

The :graphics-pkg header argument can be set to use either Maxima's built-in plot package (the default), or the draw package.

The plot package

The plot package is the default package that provides a simplified interface to gnuplot. Here is an example that creates a gif file. 

#+NAME: graphics-pkg--plot
#+HEADER: :graphics-pkg plot
#+HEADER: :file images/ob-maxima-plot.gif
#+HEADER: :results graphics file
#+HEADER: :exports both
#+begin_src maxima
plot2d( sin(x), [x,0,2*%pi]);
#+end_src

HTML export of the results:

ob-maxima-plot.gif
Figure 1: The graph of sin(x) created with plot.

The draw package

The draw package has more features than plot, including an object-oriented interface to several graphics engines, including gnuplot. Here is an example that creates an svg file containing the graph of a discontinuous function. 

#+NAME: graphics-pkg--draw
#+HEADER: :graphics-pkg draw
#+HEADER: :file images/ob-maxima-draw.svg
#+HEADER: :results graphics file
#+HEADER: :exports both
#+begin_src maxima
f(x) := if x>0 then cos(x) else if x<0 then 0;
draw2d(
  line_width=2, grid=true, yrange=[-1.2,1.2],
  explicit(f,x,0,%pi), explicit(f,x,-1,0),
  fill_color=white, ellipse(0,0,0.05,0.05,0,360),
  fill_color=blue , ellipse(0,1,0.05,0.05,0,360));
#+end_src

HTML export of the results:

ob-maxima-draw.svg
Figure 2: A discontinuous function plotted with draw.
  • Note

    Internally, ob-maxima uses the function set_draw_defaults. Because this function overwrites the existing defaults, using it in code blocks with the :graphics-pkg draw header argument will cause the source block evaluation to fail silently.

Additional Notes

Toggle inline display of latex code

Latex code in org mode can be displayed inline by 'C-c C-x C-l'. To remove the inline display 'C-c C-c' is used. This is described further in the manual 2.

Set scale of output

If the inline display of the equations are illegible, the scale can be set by customising the variable 'org-format-latex-options', by setting the :scale variable to a value >1.

Export

This exports nicely to both html (C-c C-e h h) and pdf (C-c C-e l p). See 3 and 4 in the manual.

Noweb expansion

NOTE: I have not tested this yet, but as Eric Schulte noted on the mailing list: "Alternately, if you really want to get fancy you could use noweb expansion 5 to insert the results of the imaxima code block into a latex code block, and then use the existing latex code block functionality to convert the imaxima output to images of different types depending on the export target." 6

Footnotes:

1

(info "(org)Library of Babel")

2

(info "(org)Previewing LaTeX fragments")

3

(info "(org)Exporting code blocks")

4

(info "(org)The export dispatcher")

5

(info "(org)noweb")

6

Re: imaxima babel

Documentation from the orgmode.org/worg/ website (either in its HTML format or in its Org format) is licensed under the GNU Free Documentation License version 1.3 or later. The code examples and css stylesheets are licensed under the GNU General Public License v3 or later.