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Re: A Bug in Parametric Plot ?
*To*: mathgroup at smc.vnet.net
*Subject*: [mg5376] Re: [mg5324] A Bug in Parametric Plot ?
*From*: Andrei Constantinescu <constant at athena.polytechnique.fr>
*Date*: Thu, 5 Dec 1996 14:50:18 -0500
*Sender*: owner-wri-mathgroup at wolfram.com
I might say, there is no bug in ParametricPlot !
Surely, :-) , you might say there is a bug, because you
get the nice figures as you say, and not the circle as we might
expect.
But lets look a little deeper how ParametricPlot functions:
- you give {x[t], y[t]} and {t, a, b}
- Mma samples the interval {t, a , b } and computes for each t_i
{x[t_i], y[t_i]}
- then the whole list comes in a Line object:
Line[ list_of_points={....{x[t_i], y[t_i]} , .....} ]
- and draws the line with Show & Graphics commands.
What happens when you choose a large interval ?
- the time samples are at large distances (the t_i) , and the
geometric points (the {x[t_i], y[t_i]}) are also espaced !
So that a line between two of them is more a diameter than a little
cord.
This gives the nice plot. So for special K , and special number of sampling points
you can get just a triangle !
In order to change this, try to change the PlotPoints options in ParametricPlot !
In[4]:= ParametricPlot[{Cos[t], Sin[t]} , {t, -1280 Pi, 1280 Pi},
PlotPoints -> 100 ]
Out[4]= -Graphics-
In[5]:= Warning: Cannot convert string "9x15B" to type FontStruct
ParametricPlot[{Cos[t], Sin[t]} , {t, -1280 Pi, 1280 Pi},
PlotPoints -> 300 ]
Out[5]= -Graphics-
a + andrei
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