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Re: Don't understand Plot behavior


Hi,

yes because Evaluate[] work only if it is
waraped arround a function argument or a
sequence of arguments, and you have to write

Plot[Evaluate[{f[t],0}] , {t, 0, 1}]

otherwise the List[] argument is evaluatet that
help Plot[] nothing.

Regards
  Jens

Alain Cochard wrote:
> 
> In[1]:= f[t_]:= D[t  , t]
> 
> In[2]:= Plot[Evaluate[f[t]] , {t, 0, 1}]
> 
> Out[2]= -Graphics-    [The plot is fine]
> 
> In[3]:= Plot[{Evaluate[f[t]],0} , {t, 0, 1}]
> 
>                          -8
> General::ivar: 4.16667 10   is not a valid variable.
> 
> [...]
> 
> General::stop: Further output of General::ivar
>      will be suppressed during this calculation.
> 
> Plot::plnr: Evaluate[f[t]] is not a machine-size real number at t =
>               -8
>     4.16667 10  .
> 
> [...]
> 
> General::stop: Further output of Plot::plnr
>      will be suppressed during this calculation.
> 
> Out[3]= -Graphics- [The plot just shows the axes]
> 
> In[4]:= harhar=Evaluate[f[t]]; Plot[{harhar,0} , {t, 0, 1}]
> 
> Out[4]= -Graphics- [The plot is fine]
> 
> In[5]:= $Version
> 
> Out[5]= 4.1 for Sun Solaris (November 8, 2000)
> 
> Is this behavior normal?  Thx in advance.
> 
> Alain Cochard
> al2 at noos.fr


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