PSTricks: readdata and additional data



Hi all,

drawing some diagrams I run into the problem that some of the data to display comes from a file whereas an other part of the data is calculated with LaTeX or PerlTeX.
How do I combine data coming from those different sources?
I guess there is a possibility to change the array \readdata creates. But I didn't manage to find the way to add data to the array.

\begin{pspicture}
\readdata\dataToDisplay{file.dat}
%% somehow manipulate \dataToDisplay
\listplot{\dataToDisplay}
\end{pspicture}

thanks in advance
Stephan
.