       Re: Problem with singularities in Plot3D

• To: mathgroup at smc.vnet.net
• Subject: [mg55354] Re: Problem with singularities in Plot3D
• From: Peter Pein <petsie at arcor.de>
• Date: Sun, 20 Mar 2005 04:11:47 -0500 (EST)
• References: <d1gtdv\$jh\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Steeve Brechmann (schumi) wrote:
> Hi,
>
> I have a little problem with the Plot3D command of Mathematica.
> I want to plot the 3D graphics of :
>
> eqt[q_,N_,M_]:= - (3*q/(8*Pi))*(Sum[(Cos[4*Pi*n*d]/(2*n*d))-(Sin[4*Pi*n*d]/(8*Pi*(n*d)^2))-(Cos[4*Pi*n*d]/(32*Pi^2*(n*d)^3)),{n,1,N}] - Sum[(Cos[4*Pi*Abs[z0-m*d]]/Abs[z0-m*d])-(Sin[4*Pi*Abs[z0-m*d]]/(4*Pi*Abs[z0-m*d]^2))-(Cos[4*Pi*Abs[z0-m*d]]/(16*Pi^2*Abs[z0-m*d]^3)),{m,-M,M}])
>
> Plot3D[Evaluate[eqt[1,10,10]],{z0,0,3},{d,0.1,6},PlotPoints->50];
>
> Like you see, my expression eqt[q,N,M] have some singularities at d = 0 and Abs[z0-m*d] = 0.
>
> How can i say to Mathematica that it must ignore the singularities Abs[z0-m*d] = 0 ?
>
>
> Steeve Brechmann von Brechenmacher
> Physics Department, Laval University
> steevebrechmann at yahoo.ca
>
>

If it is sufficient, to plot for z0 from 10^-6 to 3, try
Plot3D[Evaluate[eqt[1,10,10]],{z0,10^-6,3},{d,1/10,6},PlotPoints->50];

--
Peter Pein
Berlin

```

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