Using SageTeX - Tutorial

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# Using SageTeX

The SageTeX package allows you to embed the results of Sage computations into a LaTeX document. To use it, you will need to “install” it first (see Make SageTeX known to TeX).

## An example

Here is a very brief example of using SageTeX. The full documentation can be found in `SAGE_ROOT/venv/share/doc/sagetex`, where `SAGE_ROOT` is the directory where your Sage installation is located. That directory contains the documentation and an example file. See `SAGE_ROOT/venv/share/texmf/tex/latex/sagetex` for some possibly useful Python scripts.

To see how SageTeX works, follow the directions for installing SageTeX (in Make SageTeX known to TeX) and copy the following text into a file named, say, `st_example.tex`:

Warning

The text below will have several errors about unknown control sequences if you are viewing this in the “live” help. Use the static version to see the correct text.

    \documentclass{article}
    \usepackage{sagetex}

    \begin{document}

    Using Sage\TeX, one can use Sage to compute things and put them into
    your \LaTeX{} document. For example, there are
    $\sage{number_of_partitions(1269)}$ integer partitions of $1269$.
    You don't need to compute the number yourself, or even cut and paste
    it from somewhere.

    Here's some Sage code:

    \begin{sageblock}
        f(x) = exp(x) * sin(2*x)
    \end{sageblock}

    The second derivative of $f$ is

    \[
      \frac{\mathrm{d}^{2}}{\mathrm{d}x^{2}} \sage{f(x)} =
      \sage{diff(f, x, 2)(x)}.
    \]

    Here's a plot of $f$ from $-1$ to $1$:

    \sageplot{plot(f, -1, 1)}

    \end{document}

Run LaTeX on `st_example.tex` as usual. Note that LaTeX will have some complaints, which will include:

    Package sagetex Warning: Graphics file
    sage-plots-for-st_example.tex/plot-0.eps on page 1 does not exist. Plot
    command is on input line 25.

    Package sagetex Warning: There were undefined Sage formulas and/or
    plots. Run Sage on st_example.sagetex.sage, and then run LaTeX on
    st_example.tex again.

Notice that, in addition to the usual collection of files produced by LaTeX, there is a file called `st_example.sagetex.sage`. That is a Sage script produced when you run LaTeX on `st_example.tex`. The warning message told you to run Sage on `st_example.sagetex.sage`, so take its advice and do that. It will tell you to run LaTeX on `st_example.tex` again, but before you do that, notice that a new file has been created: `st_example.sagetex.sout`. That file contains the results of Sage’s computations, in a format that LaTeX can use to insert into your text. A new directory containing an EPS file of your plot has also been created. Run LaTeX again and you’ll see that everything that Sage computed and plotted is now included in your document.

The different macros used above should be pretty easy to understand. A `sageblock` environment typesets your code verbatim and also executes the code when you run Sage. When you do `\sage{foo}`, the result put into your document is whatever you get from running `latex(foo)` inside Sage. Plot commands are a bit more complicated, but in their simplest form, `\sageplot{foo}` inserts the image you get from doing `foo.save('filename.eps')`.

In general, the mantra is:

> - run LaTeX on your .tex file;

> - run Sage on the generated .sage file;

> - run LaTeX again.

You can omit running Sage if you haven’t changed around any Sage commands in your document.

There’s a lot more to SageTeX, and since both Sage and LaTeX are complex, powerful tools, it’s a good idea to read the documentation for SageTeX, which is in `SAGE_ROOT/venv/share/doc/sagetex`.

## Make SageTeX known to TeX

Sage is largely self-contained, but some parts do need some intervention to work properly. SageTeX is one such part.

The SageTeX package allows one to embed computations and plots from Sage into a LaTeX document. SageTeX is installed in Sage by default, but to use SageTeX with your LaTeX documents, you need to make your TeX installation aware of it before it will work.

The key to this is that TeX needs to be able to find `sagetex.sty`, which can be found in `SAGE_ROOT/venv/share/texmf/tex/latex/sagetex/`, where `SAGE_ROOT` is the directory where you built or installed Sage. If TeX can find `sagetex.sty`, then SageTeX will work. There are several ways to accomplish this.

- The first and simplest way is simply to copy `sagetex.sty` into the same directory as your LaTeX document. Since the current directory is always searched when typesetting a document, this will always work.

  There are a couple small problems with this, however: the first is that you will end up with many unnecessary copies of `sagetex.sty` scattered around your computer. The second and more serious problem is that if you upgrade Sage and get a new version of SageTeX, the Python code and LaTeX code for SageTeX may no longer match, causing errors.

- The second way is to use the `TEXMFLOCAL` environment variable. If you are using the bash shell, you can do

      $ export TEXMFLOCAL=SAGE_ROOT/venv/share/texmf
      $ mktexlsr       # update kpathsea ls-R databases

  where `SAGE_ROOT` is the location of your Sage installation. Thereafter, TeX and friends will find the SageTeX style file. If you want to make this change persistent, you can add the 1st of the above lines to your `.bashrc` file. If you are using a different shell, you may have to modify the above command to make the environment variable known; see your shell’s documentation for how to do that.

  If you ever move your Sage installation, or install a new version into a new directory, you’ll need to update the above command to reflect the new value of `SAGE_ROOT`.

- The third (and best) way to make TeX aware of `sagetex.sty` is to copy that file into a convenient place in your home directory. In most TeX distributions, the `texmf` directory in your home directory is automatically searched for packages. To find out exactly what this directory is, do the following on the command line:

      $ kpsewhich -var-value=TEXMFHOME

  which will print out a directory, such as `/home/drake/texmf` or `/Users/drake/Library/texmf`. Copy the `tex/` directory from `SAGE_ROOT/venv/share/texmf/` into your home `texmf` directory with a command like

      $ cp -R SAGE_ROOT/venv/share/texmf/tex TEXMFHOME

  where `SAGE_ROOT` is, as usual, replaced with the location of your Sage installation and `TEXMFHOME` is the result of the `kpsewhich` command above.

  If you upgrade Sage and discover that SageTeX no longer works, you can simply repeat these steps and the Sage and TeX parts of SageTeX will again be synchronized.

- For installation on a multiuser system, you just modify the above instructions appropriately to copy `sagetex.sty` into a systemwide TeX directory. Instead of the directory `TEXMFHOME`, probably the best choice is to use the result of

      $ kpsewhich -var-value=TEXMFLOCAL

  which will likely produce something like `/usr/local/share/texmf`. Copy the `tex` directory as above into the `TEXMFLOCAL` directory. Now you need to update TeX’s database of packages, which you can do simply by running

      $ texhash TEXMFLOCAL

  as root, replacing `TEXMFLOCAL` appropriately. Now all users of your system will have access to the LaTeX package, and if they can also run Sage, they will be able to use SageTeX.

Warning

it’s very important that the file `sagetex.sty` that LaTeX uses when typesetting your document match the version of SageTeX that Sage is using. If you upgrade your Sage installation, you really should delete all the old versions of `sagetex.sty` floating around.

Because of this problem, we recommend copying the SageTeX files into your home directory’s texmf directory (the third method above). Then there is only one thing you need to do (copy a directory) when you upgrade Sage to insure that SageTeX will work properly.

## SageTeX documentation

While not strictly part of installation, it bears mentioning here that the documentation for SageTeX is maintained in `SAGE_ROOT/venv/share/doc/sagetex/sagetex.pdf`. There is also an example file in the same directory – see `example.tex` and `example.pdf`, the pre-built result of typesetting that file with LaTeX and Sage. You can also get those files from the SageTeX page.

## SageTeX and TeXLive

One potentially confusing issue is that the popular TeX distribution TeXLive includes SageTeX. This may seem nice, but with SageTeX, it’s important that the Sage bits and LaTeX bits be synchronized – which is a problem in this case, since TeXLive, as shipped by your OS distro, or package manager, might be out of sync with TeXLive distribution, and the latter might also be out of sync with the current SageTeX.

Because of this, it is strongly recommended that you always install the LaTeX part of SageTeX from Sage, as described above. The instructions above will insure that both halves of SageTeX are compatible and will work properly.