derivatives of indexed variables

*Subject*: [mg2626] derivatives of indexed variables*From*: george at mech.seas.upenn.edu ( George Jefferson )*Date*: Sun, 3 Dec 1995 02:51:57 -0500*Approved*: usenet@wri.com*Distribution*: local*Newsgroups*: wri.mathgroup*Organization*: Wolfram Research, Inc.

What am I missing? total derivative of unspecified y: In[1]:= Dt[y,x] Out[1]= Dt[y, x] But if we take the derivaitve of an undefined indexed variable it is assumed to be a constant.. In[2]:= Dt[a[1],x] Out[2]= 0 note however that the indexed symbol could easily represent a non-constant. In[3]:= a[1]=y; Dt[a[1],x] Out[3]= Dt[y, x] clearly the trouble is that there is no distinction between an indexed symbol and a function evaluated at a fixed point.. Is there a workaround?