Re: RecurrenceTable warning

*To*: mathgroup at smc.vnet.net*Subject*: [mg102494] Re: [mg102430] RecurrenceTable warning*From*: dkapadia at wolfram.com*Date*: Tue, 11 Aug 2009 04:04:51 -0400 (EDT)*References*: <200908091005.GAA15916@smc.vnet.net>

> Hello, I'm using Mathematica 7.0.1. > > This example is in documentation center. > > In[1]:= RecurrenceTable[{a[n + 1] == 3 a[n], a[1] == 7}, a, {n, 1, 5}] > Out[1]= {7, 21, 63, 189, 567} > > > I added a[n]==b[n]. > > In[2]:= RecurrenceTable[{b[n] == a[n], a[n + 1] == 3 a[n], > a[1] == 7}, {a, b}, {n, 1, 5}] > Out[2]= {{7, 7}, {21, 21}, {63, 63}, {189, 189}, {567, 567}} > > > it works well. > but when I simply swapped a with b, a warning occured. > > In[3]:= RecurrenceTable[{a[n] == b[n], b[n + 1] == 3 b[n], > b[1] == 7}, {b, a}, {n, 1, 5}] > > During evaluation of In[3]:= Inverse::matsq: Argument {{1/4,1,-1}, > {1/4,0,1}} at position 1 is not a non-empty square matrix. >> > > Out[3]= {{7, 7}, {21, 21}, {63, 63}, {189, 189}, {567, 567}} > > Hello, Thank you for reporting the above problem with RecurrenceTable. The unexpected Inverse::matsq message is generated while trying to solve the equations with a and b swapped, as a system of difference-algebraic equations. I apologize for the confusion caused by this problem, which clearly needs to be fixed. Sincerely, Devendra Kapadia, Wolfram Research, Inc.

**References**:**RecurrenceTable warning***From:*green tea <cetech07@gmail.com>