      \fitem{gnuplot}(title1:string, time1:tab, data1:tab, title2: string,
      time2:tab, data2:tab, ...): %
      \label{gnuplot:forme5} %%
      In this variant, several curves are plotted in the same window. One
      curve is specified by 2 or 3 consecutive arguments. Three arguments
      are used if the first considered argument is a string: in this case,
      this argument is the label of the curve. The following argument is
      used as the $x$ coordinates and the next one as the $y$ coordinates
      of the plotted point.
      
      In this variant, the \code{data}$i$ arguments must be tab of numeric
      values (they cannot be tab of tab). 




      %%% -------------------------------------------------------

