Minh Nguyen wrote:
> Hi Mani,
>
> On Thu, Aug 13, 2009 at 6:08 PM, Mani chandra<mchan...@iitk.ac.in> wrote:
>
>> Hi,
>>
>> I have a set of variables which I defined in an array and I'm trying
>> to use "solve" to solve for these variables, but I get the following error:
>>
>> x = []
>> N = 3
>> for i in range(N):
>> string = 'x' + str(i)
>> temp_var = var(string)
>> x.append(temp_var)
>> Eqn = []
>> Eqn.append(x[0] + x[1] + x[2])
>> Eqn.append(x[0] - x[1] + x[2])
>>
>> solve([Eqn[1]==0], x[1], solution_dict=True)
>>
>> Traceback (most recent call last):
>> File "<stdin>", line 1, in <module>
>> File "/home/mc/.sage/sage_notebook/worksheets/admin/7/code/47.py", line 17,
>> in <module>
>> solve([Eqn[_sage_const_1 ]==_sage_const_0 ], x[_sage_const_1 ],
>> solution_dict=True)
>> File "", line 1, in <module>
>>
>> File
>> "/opt/sage/sage/local/lib/python2.6/site-packages/sage/symbolic/relation.py",
>> line 509, in solve
>> sol_dict=[dict([[eq.left(),eq.right()] for eq in solution]) for solution
>> in sol_list]
>>
>>
>> TypeError: 'sage.symbolic.expression.Expression' object is not iterable
>>
>>
>> However the following seems to work:
>>
>> solve([Eqn[1]==0], x[1])
>>
>>
>> [x1 == x0 + x2]
>>
>> The reason I need solution_dict=True is that I need to put the solution
>> in x[1], which solve does not do. Could someone please help me out?
>>
>
> Is the following what you're trying to do?
>
> ----------------------------------------------------------------------
> | Sage Version 4.1, Release Date: 2009-07-09 |
> | Type notebook() for the GUI, and license() for information. |
> ----------------------------------------------------------------------
> sage: x = []
> sage: N = 3
> sage: for i in xrange(N):
> ....: string = "x" + str(i)
> ....: temp_var = var(string)
> ....: x.append(temp_var)
> ....:
> sage: Eqn = []
> sage: Eqn.append(x[0] + x[1] + x[2])
> sage: Eqn.append(x[0] - x[1] + x[2])
> sage: solve(Eqn[1] == 0, x[1], solution_dict=True)
> [{x1: x0 + x2}]
>
> You only had one equation to solve and you wanted to get the solution
> dictionary for the solution of that one equation. In that case, you
> don't need to put that equation in a list. So instead of
>
> [Eqn[1] == 0]
>
> I changed it to
>
> Eqn[1] == 0
>
> If you have more than one equation to solve, then you can put those
> equations in a list. The solve() command would then interpret the list
> of equations as a system of simultaneous equations. For example:
>
> sage: solve([Eqn[1] == 0, Eqn[0] == 0], [x[1], x[0]], solution_dict=True)
> [{x1: 0, x0: -x2}]
>
>
Thank you for that, solved my problem!
Mani chandra
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