\subsection{plot}
\label{labplot}
\noindent Name: \textbf{plot}\\
\phantom{aaa}plots one or several functions\\[0.2cm]
\noindent Library names:\\
\verb|   void sollya_lib_plot(sollya_obj_t, sollya_obj_t, ...)|\\
\verb|   void sollya_lib_v_plot(sollya_obj_t, sollya_obj_t, va_list)|\\[0.2cm]
\noindent Usage: 
\begin{center}
\textbf{plot}(\emph{f1}, ... ,\emph{fn}, \emph{I}) : (\textsf{function}, ... ,\textsf{function}, \textsf{range}) $\rightarrow$ \textsf{void}\\
\textbf{plot}(\emph{f1}, ... ,\emph{fn}, \emph{I}, \textbf{file}, \emph{name}) : (\textsf{function}, ... ,\textsf{function}, \textsf{range}, \textbf{file}, \textsf{string}) $\rightarrow$ \textsf{void}\\
\textbf{plot}(\emph{f1}, ... ,\emph{fn}, \emph{I}, \textbf{postscript}, \emph{name}) : (\textsf{function}, ... ,\textsf{function}, \textsf{range}, \textbf{postscript}, \textsf{string}) $\rightarrow$ \textsf{void}\\
\textbf{plot}(\emph{f1}, ... ,\emph{fn}, \emph{I}, \textbf{postscriptfile}, \emph{name}) : (\textsf{function}, ... ,\textsf{function}, \textsf{range}, \textbf{postscriptfile}, \textsf{string}) $\rightarrow$ \textsf{void}\\
\textbf{plot}(\emph{L}, \emph{I}) : (\textsf{list}, \textsf{range}) $\rightarrow$ \textsf{void}\\
\textbf{plot}(\emph{L}, \emph{I}, \textbf{file}, \emph{name}) : (\textsf{list}, \textsf{range}, \textbf{file}, \textsf{string}) $\rightarrow$ \textsf{void}\\
\textbf{plot}(\emph{L}, \emph{I}, \textbf{postscript}, \emph{name}) : (\textsf{list}, \textsf{range}, \textbf{postscript}, \textsf{string}) $\rightarrow$ \textsf{void}\\
\textbf{plot}(\emph{L}, \emph{I}, \textbf{postscriptfile}, \emph{name}) : (\textsf{list}, \textsf{range}, \textbf{postscriptfile}, \textsf{string}) $\rightarrow$ \textsf{void}\\
\end{center}
Parameters: 
\begin{itemize}
\item \emph{f1}, ..., \emph{fn} are functions to be plotted.
\item \emph{L} is a list of functions to be plotted.
\item \emph{I} is the interval where the functions have to be plotted.
\item \emph{name} is a string representing the name of a file.
\end{itemize}
\noindent Description: \begin{itemize}

\item This command plots one or several functions \emph{f1}, ... ,\emph{fn} on an
   interval \emph{I}. Functions can be either given as parameters of \textbf{plot} or as a
   list \emph{L} which elements are functions.
   The functions are drawn on the same plot with different colors.

\item If \emph{L} contains an element that is not a function (or a constant), an error
   occurs.

\item \textbf{plot} relies on the value of global variable \textbf{points}. Let $n$ be the 
   value of this variable. The algorithm is the following: each function is 
   evaluated at $n$ evenly distributed points in \emph{I}. At each point, the 
   computed value is a faithful rounding of the exact value with a sufficiently
   high precision. Each point is finally plotted.
   This should avoid numerical artefacts such as critical cancellations.

\item The plot can be saved either as a data file or as a postscript file.

\item If you use argument \textbf{file} with a string \emph{name}, \sollya will save a data file
   called name.dat and a gnuplot directives file called name.p. Invoking gnuplot
   on name.p will plot the data stored in name.dat.

\item If you use argument \textbf{postscript} with a string \emph{name}, \sollya will save a 
   postscript file called name.eps representing your plot.

\item If you use argument \textbf{postscriptfile} with a string \emph{name}, \sollya will 
   produce the corresponding name.dat, name.p and name.eps.

\item By default, this command uses gnuplot to produce the final plot. If \sollya
   is run while the environment variable \verb|SOLLYA_GNUPLOT| is set, the content of
   that variable is used as the gnuplot binary.
   If your terminal is not graphic (typically if you use \sollya through 
   ssh without -X)
   gnuplot should be able to detect that and produce an ASCII-art version on the
   standard output. If it is not the case, you can either store the plot in a
   postscript file to view it locally, or use \textbf{asciiplot} command.

\item If every function is constant, \textbf{plot} will not plot them but just display
   their value.

\item If the interval is reduced to a single point, \textbf{plot} will just display the
   value of the functions at this point.
\end{itemize}
\noindent Example 1: 
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> plot(sin(x),0,cos(x),[-Pi,Pi]);
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 2: 
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> plot(sin(x),0,cos(x),[-Pi,Pi],postscriptfile,"plotSinCos");
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 3: 
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> plot(exp(0), sin(1), [0;1]);
1
0.84147098480789650665250232163029899962256306079837
\end{Verbatim}
\end{minipage}\end{center}
\noindent Example 4: 
\begin{center}\begin{minipage}{15cm}\begin{Verbatim}[frame=single]
> plot(sin(x), cos(x), [1;1]);
0.84147098480789650665250232163029899962256306079837
0.54030230586813971740093660744297660373231042061792
\end{Verbatim}
\end{minipage}\end{center}
See also: \textbf{externalplot} (\ref{labexternalplot}), \textbf{asciiplot} (\ref{labasciiplot}), \textbf{file} (\ref{labfile}), \textbf{postscript} (\ref{labpostscript}), \textbf{postscriptfile} (\ref{labpostscriptfile}), \textbf{points} (\ref{labpoints})
