#2473 polar graphs are wrong

[Manuel González-Hidalgo]

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build_info("5.28.0-2","2012-08-27 23:16:48","i686-pc-mingw32","GNU Common Lisp (GCL)","GCL 2.6.8")
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If I put in the console

wxplot2d(t, [t,0,4*%pi],[plot_format, gnuplot],
[gnuplot_preamble, "set polar; set trange [0:4*pi]; set rrange [0:4*pi];"])$

we obtain a incorrect plot of the function as we can see in the attached image.

If I put in the gnuplot:
set polar;
set rrange [0:4*pi];
set trange [0:4*pi];
plot t;

I obtain a coorect plot of the function. But in any case, that is for any function in polar coordinates, in Maxima the graph of the function isn't correct.

Thank you very much for your attention, and waiting for a solution to this problem, says goodbye with a greeting and best wishes

Manuel González
Prof. University of the Balearic Islands

[Manuel González-Hidalgo]

Polar plot of f(t)=t, in [0,4*pi]

[Aleksas]

All correct. Do

(%i1) wxplot2d([ph], [ph,0,4*%pi],[y,-4*%pi,4*%pi],
[gnuplot_preamble, "set polar; set zeroaxis;"],
[xlabel, ""],[ ylabel, ""])$
(%t1) << Graphics >>

or

(%i2) load(draw)$
(%i3) wxdraw2d(user_preamble = "set grid polar",
nticks = 200,
grid=true,
xrange = [-12,12], yrange = [-12,12],
color = blue, line_width = 2,
title = "Spiral",
polar(theta,theta,0,4*%pi),
proportional_axes = xy
)$
(%t3) << Graphics >>

best

Aleksas D

[Jaime E. Villate]

This is not really a bug as Aleksas has shown. Polar plots are currently not implemented in plot2d; plot2d options should work correctly with the default preamble; if the user wants to define his own gnuplot_preamble to get features missing in plot2d, he should be aware that the way plot2d options are normally used might need to be adapted to the new preamble.