Uwe,

In my testing (using octave since I don't have matlab, but I hope it's similar), using = :exports none :results output raw= seems to produce the desired output:

#+begin_src octave :exports results :results output raw
close all
N = 3; % number of chebyshev nodes
n = 1; % polytropic index
iters = 1; % iterations
j=[0 1 2 3];
z=cos((pi*j)/3);
y=1-(0.5*(z+1)).^2;
a=n*(8);
a2=eye(3+1)*a;
disp('\begin{align*}')
disp('A_{1,k-1}&=')
disp('\begin{pmatrix}')
fprintf('%g &%g &%g &%g\\\\\n',a2')
disp('\end{pmatrix}=OK\\')
disp('\end{align*}')
#+end_src

#+RESULTS:
\begin{align*}
A_{1,k-1}&=
\begin{pmatrix}
8 &0 &0 &0\\
0 &8 &0 &0\\
0 &0 &8 &0\\
0 &0 &0 &8\\
\end{pmatrix}=OK\\
\end{align*}

Which renders the matrix correctly. I first tried with =:exports results=, but that for some reason results in the results being included twice in the LaTeX output. I'm not sure why.

Hope this helps,

--Diego

On Tue, Oct 13, 2020 at 1:36 PM Uwe Brauer <oub@mat.ucm.es> wrote:

>>> "AB" == Arne Babenhauserheide <arne_bab@web.de> writes:

> Uwe Brauer <oub@mat.ucm.es> writes:

>> That did not work: I tried
>> #+begin_src matlab :results output
>>
>> But when I exported the org file to latex, the matlab code was also
>> exported. Strange

> Do you use :exports results?

> :results output switches to show what is printed to stdout

See my answer to Eric

It does not do want I want
#+begin_src matlab :exports results
close all
N = 3; % number of chebyshev nodes
n = 1; % polytropic index
iters = 1; % iterations
j=[0 1 2 3];
z=cos((pi*j)/3);
y=1-(0.5*(z+1)).^2;
a=n*(8);
a2=eye(3+1)*a;
disp('\begin{align*}')
disp('A_{1,k-1}&=')
disp('\begin{pmatrix}')
fprintf('%g &%g &%g &%g\\\\\n',a2')
disp('\end{pmatrix}=OK\\')
disp('\end{align*}')
#+end_src

Leads to

\begin{verbatim}
\begin{align*}
A_{1,k-1}&=
\begin{pmatrix}
8 &0 &0 &0\\
0 &8 &0 &0\\
0 &0 &8 &0\\
0 &0 &0 &8\\
\end{pmatrix}=OK\\
\end{align*}
\end{verbatim}

So at the moment the only solution I can think of is to use the code I
posted

(defun my-latex-filter-src-blocks (text backend info)
"Remove source blocks from latex export."
(when (org-export-derived-backend-p backend 'latex)
"%% [removed source block]\n"))

(add-to-list 'org-export-filter-src-block-functions
'my-latex-filter-src-blocks)