Re: Don't understand Plot behavior

• To: mathgroup at smc.vnet.net
• Subject: [mg39994] Re: [mg39971] Don't understand Plot behavior
• From: Ken Levasseur <klevasseur at mac.com>
• Date: Fri, 14 Mar 2003 04:45:32 -0500 (EST)
• Sender: owner-wri-mathgroup at wolfram.com

```Alain:

Evaluate needs to be at the top level of the first argument of plot to have
the effect that it has in your first example.

This is what happens in your first example
In[11]:=
Hold[Evaluate[f[t]]]

Out[11]=
Hold[t^2]

Now the second:
In[12]:=
Hold[{Evaluate[f[t]], 0}]

Out[12]=
Hold[{Evaluate[f[t]], 0}]

If you rearrange the the expression, you get what you want:

In[13]:=
Hold[Evaluate[{f[t], 0}]]

Out[13]=
Hold[{t^2, 0}]

Ken Levasseur
UMass Lowell

> From: Alain Cochard <al2 at noos.fr>
To: mathgroup at smc.vnet.net
> Date: Thu, 13 Mar 2003 03:03:58 -0500 (EST)
> To: mathgroup at smc.vnet.net
> Subject: [mg39994] [mg39971] Don't understand Plot behavior
>
>
> 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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