Don't understand Plot behavior

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

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