       # Re: Drawing multiple curves with ParametricPlot3D

```Volker Doerr wrote:

>
> I want to display two curves from six InterpolatingFunctions
>
>   {r1x[t], r1y[t], r1z[t], r2x[t], r2y[t], r2z[t]}
>
> produced with NDSolve. The documentation describes the  usage of
> ParametricPlot3D for displaying one curve:
>
>   ParametricPlot3D[{fx,fy,fz},{t,tmin,tmax}]
>
> and this works fine for me:
>
>   ParametricPlot3D[Evaluate[{r1x[t],r1y[t],r1z[t]}/.%],{t,0,dt}]
>
> For plotting several objects together,  the documentation says:
>
>   ParametricPlot3D[{{fx,fy,fz},{gx,gy,gz},...},...]
>
> but
>
>   ParametricPlot3D[
>     {Evaluate[{r1x[t],r1y[t],r1z[t]}/.%],
>      Evaluate[{r2x[t],r2y[t],r2z[t]}/.%],{t,0,dt}},{t,0,dt}]
>
> doesn't work at all. I tried to vary this expression in many (also
> stupid) ways, without any result. What's wrong with it?
>

Volker: just move the Evaluate outside the list - to be effective in
cancelling the HoldAll attribute, Evaluate must be round the argument
that is being held:

sol =NDSolve[{x'[t] == Cos[t],x==0}, x[t],{t,0,7}];

ParametricPlot3D[Evaluate[{{x[t],x[t]^2,x[t]^3},
{x[t]^3,x[t]^2,x[t]}}/.sol[]], {t,0,7}];

--
Allan Hayes
Training and Consulting
Leicester, UK
hay@haystack.demon.co.uk
http://www.haystack.demon.co.uk
voice: +44 (0)116 271 4198
fax: +44 (0)116 271 8642

```

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