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- Executable file
r38/doc/manual2/gnuplot.tex
— part of check-in
[f2fda60abd]
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2011-09-02 18:13:33
on branch master
— Some historical releases purely for archival purposes
git-svn-id: https://svn.code.sf.net/p/reduce-algebra/code/trunk/historical@1375 2bfe0521-f11c-4a00-b80e-6202646ff360 (user: arthurcnorman@users.sourceforge.net, size: 4086) [annotate] [blame] [check-ins using]
\chapter[GNUPLOT: Plotting Functions]% {GNUPLOT: Display of functions and surfaces} \label{GNUPLOT} \typeout{{GNUPLOT: Display of functions and surfaces}} {\footnotesize \begin{center} Herbert Melenk \\ Konrad--Zuse--Zentrum f\"ur Informationstechnik Berlin \\ Takustra\"se 7 \\ D--14195 Berlin--Dahlem, Germany \\[0.05in] e--mail: melenk@zib.de \end{center} } \ttindex{GNUPLOT} The {\bf gnuplot} system provides easy to use graphics output for curves or surfaces which are defined by formulas and/or data sets. The \REDUCE\ GNUPLOT package lets one use the GNUPLOT graphical output directly from inside \REDUCE, either for the interactive display of curves/surfaces or for the production of pictures on paper. For a full understanding of use of the \REDUCE\ GNUPLOT package it is best to be familiar with {\bf gnuplot}. The main command is {\tt PLOT}\ttindex{PLOT}. It accepts an arbitrary list of arguments which are either an expression to be plotted, a range expressions or an option. \begin{verbatim} load_package gnuplot; plot(w=sin(a),a=(0 .. 10),xlabel="angle",ylabel="sine"); \end{verbatim} The expression can be in one or two unknowns, or a list of two functions for the x and y values. It can also be an implicit equation in 2-dimensional space. \begin{verbatim} plot(x**3+x*y**3-9x=0); \end{verbatim} The dependent and independent variables can be limited to a range with the syntax shown in the first example. If omitted the independent variables range from -10 to 10 and the dependent variable is limited only by the precision of the IEEE floating point arithmetic. There are a great deal of options, either as keywords or as {\tt variable=string}. Options include: {\tt title}\ttindex{title}: assign a heading (default: empty) {\tt xlabel}\ttindex{xlabel}: set label for the x axis {\tt ylabel}\ttindex{ylabel}: set label for the y axis {\tt zlabel}\ttindex{zlabel}: set label for the z axis {\tt terminal}\ttindex{terminal}: select an output device {\tt size}\ttindex{size}: rescale the picture {\tt view}\ttindex{view}: set a viewpoint {\tt (no)}{\tt contour}\ttindex{contour}: 3d: add contour lines {\tt (no)}{\tt surface}\ttindex{surface}: 3d: draw surface (default: yes) {\tt (no)}{\tt hidden3d}\ttindex{hidden3d}: 3d: remove hidden lines (default: no) The command {\tt PLOTRESET}\ttindex{PLOTRESET} closes the current GNUPLOT windows. The next call to {\tt PLOT} will create a new one. GNUPLOT is controlled by a number of switches. Normally all intermediate data sets are deleted after terminating a plot session. If the switch {\tt PLOTKEEP}\ttindex{PLOTKEEP} is set on, the data sets are kept for eventual post processing independent of \REDUCE. In general {\tt PLOT} tries to generate smooth pictures by evaluating the functions at interior points until the distances are fine enough. This can require a lot of computing time if the single function evaluation is expensive. The refinement is controlled by the switch {\tt PLOTREFINE}\ttindex{PLOTREFINE} which is on by default. When you turn it off the functions will be evaluated only at the basic points. The integer value of the global variable {\tt PLOT\_XMESH}\ttindex{PLOT\_XMESH} defines the number of initial function evaluations in x direction for \f{PLOT}. For 2d graphs additional points will be used as long as {\tt plotrefine}\ttindex{plotrefine} is on. For 3d graphs this number defines also the number of mesh lines orthogonal to the x axis. {\tt PLOT\_YMESH}\ttindex{PLOT\_YMESH} defines for 3d plots the number of function evaluations in the y direction and the number of mesh lines orthogonal to the y axis. The grid for localising an implicitly defined curve in \f{PLOT} consists of triangles. These are computed initially equally distributed over the x-y plane controlled by {\tt PLOT\_XMESH}. The grid is refined adaptively in several levels. The final grid can be visualised by setting on the switch {\tt SHOW\_GRID}\ttindex{SHOW\_GRID}.