Re: Collect coefficients of array variables during calculation:

*To*: mathgroup at smc.vnet.net*Subject*: [mg87064] Re: Collect coefficients of array variables during calculation:*From*: Szabolcs Horvát <szhorvat at gmail.com>*Date*: Sun, 30 Mar 2008 01:19:15 -0500 (EST)*Organization*: University of Bergen*References*: <fsib0m$5qe$1@smc.vnet.net>

Gopinath Venkatesan wrote: > Hello Mathematica Friends > > If we have an array variable, and assuming after intermediate calculations, some equations are found to be below. > > eqn1=10. A[[1,1]]+b A[[1,1]]+c A[[1,2]]+3. A[[1,2]] (only for illustration) > > Simplify[] does not combine the coefficients under same array member, i.e. instead of (10.+b)A[[1,1]]+(c+3.)A[[1,2]], it is showing the earlier mentioned form. > > Is there a way to collect them and simplify them. But when I checked for simple cases, Simplify[] seems to work. Actually Simplify[] does collect the terms without additional effort: In[1]:= eqn1 = 10. A[[1, 1]] + b A[[1, 1]] + c A[[1, 2]] + 3. A[[1, 2]] During evaluation of In[1]:= Part::partd: Part specification A[[1,1]] \ is longer than depth of object. >> During evaluation of In[1]:= Part::partd: Part specification A[[1,1]] \ is longer than depth of object. >> During evaluation of In[1]:= Part::partd: Part specification A[[1,2]] \ is longer than depth of object. >> During evaluation of In[1]:= General::stop: Further output of \ Part::partd will be suppressed during this calculation. >> Out[1]= 10. A[[1, 1]] + b A[[1, 1]] + 3. A[[1, 2]] + c A[[1, 2]] In[2]:= Simplify[eqn1] Out[2]= (10.+ b) A[[1, 1]] + (3.+ c) A[[1, 2]] This still doesn't change the fact that this usage of Part ([[ ... ]]) is /incorrect/, though.