gnuplot-info

[Gnuplot-info] Cone in parametric :-)

[Carles P. i E. <ca...@pi...>]

Hello,

I am not able to plot cylinder using cartesian system (I think that is
not possible in gnuplot?)

I am trying to do the figures that I need using parametric coordinate. I
have done without problemes sphere, cylinder but I need cone. 

Here for example:
http://mathworld.wolfram.com/Cone.html

There is the parametric equations (equations number 1, 2 and 3). 

I do in gnuplot:
set parametric
set isosample 51
set ticslevel 0
h=2.0
r=1.0
splot ((h-u)/h)*r*cos(u), ((h-u)/h)*r*sin(u),v
pause -1

And something appears but doesn't look as a cone :-)

Any idea? the formula seems correct, Maybe range problem for u and v?

Thank you very much,

-- 
Carles Pina i Estany		GPG id: 0x8CBDAE64
	http://pinux.info	Manresa - Barcelona

Re: [Gnuplot-info] Cone in parametric :-)

[<HBB...@t-...>]

Carles Pina i Estany wrote:
> Hello,
> 
> I am not able to plot cylinder using cartesian system (I think that is
> not possible in gnuplot?)

You think incorrectly.

> I am trying to do the figures that I need using parametric coordinate. 

You're confusing things here.  There's no such thing as "parametric 
coordinates".  Parametric is a model for describing surfaces, not a 
coordinate system.  Gnuplot does parametric plots in a cartesian 
coordinate system.  A simple cylinder is

	set parametric
	set urange [0:2*pi]; set vrange [-2:2]
	splot cos(u), sin(u), v title "cylinder"


> Any idea? the formula seems correct, Maybe range problem for u and v?

Quite certainly, since you didn't specify any ranges for u and v. 
Please do read the documentation: "help parametric".

Re: [Gnuplot-info] Cone in parametric :-)

[Carles P. i E. <ca...@pi...>]

Hi,

On Jan/18/2007, Hans-Bernhard Br=F6ker wrote:

> >I am trying to do the figures that I need using parametric coordinate.=
=20
>=20
> You're confusing things here.  There's no such thing as "parametric=20
> coordinates".  Parametric is a model for describing surfaces, not a=20

correct, I was confusing it. My blame

> coordinate system.  Gnuplot does parametric plots in a cartesian=20
> coordinate system.  A simple cylinder is
>=20
> 	set parametric
> 	set urange [0:2*pi]; set vrange [-2:2]
> 	splot cos(u), sin(u), v title "cylinder"

iep, it works (of course). Now I can do my figures in two ways :-)
Thanks!

> >Any idea? the formula seems correct, Maybe range problem for u and v?
>=20
> Quite certainly, since you didn't specify any ranges for u and v.=20
> Please do read the documentation: "help parametric".

I was in hurry and I miss-understood, now is fine!

Sorry for the stupid mistakes: error with u and v in some formula,
divide two integers and expect a float and this...

--=20
Carles Pina i Estany		GPG id: 0x8CBDAE64
	http://pinux.info	Manresa - Barcelona