Maybe I'm misunderstanding, but it seems you look at solve(a,b) as a function to return the solution of the linear symbolic equation: a * x = b (whose solution is: x = b / a), with x scalar.
Instead, solve(a,b) gives the numerical solution of the linear system a * x = b, with x and b 1d-arrays and a 2d-array. For examples, something like:
2 * x1 + 3 * x2 = 4
4 * x1 + 5 * x2 = 6
where x = [x1, x2], b = [4, 6] and a = [[2, 3], [4, 5]]. solve(a,b) returns [-1, 2].
If from the file you import a string with the symbolic representation of you equation, and you want to solve it symbolically, stay with simpy.
hth,
L.
On 11/6/07, Eduardo Rodrigues <elr1979@gmail.com> wrote:
If I want to solve an equation with linalg.solve I must know the equation, right?
From help:
"solve(a, b)
Return the solution of a*x = b"
But if I don't know - or if I don't want to look - the equation for x, how can I solve it?
I will import equations from a file.
[]'s.
----- Original Message -----
Sent: Tuesday, November 06, 2007 10:42 AM
Subject: Re: [SciPy-user] Solve
These examples for solving equations are in scipy_tutorial.pdf
from scipy import mat, linalg
"""
Solves three simultaneous equations:
x + 3y + 5z = 10
2x + 5y + z = 8
2x + 3y + 8z =3
"""
XYparameters = mat('[1 3 5; 2 5 1; 2 3 8]')
constants = mat('[10; 8; 3]')
print linalg.solve( XYparameters, constants )
# array([[-9.28],
# [ 5.16],
# [ 0.76]])
"""
Solves two simultaneous equations:
5x + 2y - 9 = 0
3x + 4y - 4 = 0
"""
XYparameters = mat('[5 2; 3 4]')
constants = mat('[9; 4]')
print linalg.solve( XYparameters, constants ) # should print (2,-
0.5)
Eduardo Rodrigues <elr1979@gmail.com> wrote:
Hi, I am starting in Python. I usually use Maple and I am with a problem to
do the same project in Python.
I would like to solve an equation like x+y+1=0 for x. In Maple I use
"solve(x+y+1=0,x);".
Do exist a similar command in Python/NumPy/SciPy?
Regards,
Eduardo.
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