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Re: How to evaulate a function and graph it

  • To: mathgroup at smc.vnet.net
  • Subject: [mg43235] Re: How to evaulate a function and graph it
  • From: "Peter Pein" <peter1963 at totalise.co.uk>
  • Date: Wed, 20 Aug 2003 22:25:56 -0400 (EDT)
  • References: <bht3hi$n22$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

"Rebeca Choy" <rchoy at ula.ve> schrieb im Newsbeitrag
news:bht3hi$n22$1 at smc.vnet.net...
> Hi everyone,
>
> How can I evaluate a function of 2 variables, say:
>
> f(x,y) = x^4 + 3 x^2 + 5 y^2 + x + y
>
> in an interval of [-3.0,4.0] and[-3.0,4.3] for x and y?
>
> I need all the points between these two ranges to plot it
>
>
> Thanks
>
> Rebeca
>
Hi Rebecca,

All points? That would last far too long (approx. 1.3 to 2.02 eternities
;-) ).
I suggest a finite grid.

f[x_,y_]:=x^4 + 3 x^2 + 5 y^2 + x + y
Table[{x,y,f[x,y]},{y,-3,4.3,0.1},{x,-3,4,0.1}]
will give you 74*71=5254 Points. You can alter the stepsize, to get more or
less points.
If you don't have to plot it by hand, I suggest
Plot3D[x^4 + 3 x^2 + 5 y^2 + x + y,{x,-3,4},{y,-3,4.3}] (* see online help
for options *)

Peter



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