On Thu, Jul 5, 2012 at 5:56 PM, Andrew <[email protected]> wrote:
> Hi, I am very new to sympy and python, so pardon my simple question
>
> I have a matrix right here like this (4 equations, 3 unknowns)
> mat1=
> [ 0, 15.0, 10.0, 700.0]
> [ 1, 1, 1, 100.0]
> [ 0, 10.0, 5.0, 200.0]
> [-5.0, 0, 0, 0]
>
> and a list of unknowns
> unknown=[y0,y1,y2]
>
Which columns do those variables correspond to? If you multiply the
matrix by a length-4 column vector of variables and pass this to solve
it gives
>>> v = var('a:d')
>>> v
(a, b, c, d)
>>> v = Matrix([list(v)]).T
>>> e=m*v
>>> solve(e)
{c: -160.0*d, b: 60.0*d, a: 0}
And the determinant of the matrix is 0:
>>> m.det()
0
So it looks like there are infinite solutions. I don't spend much time
working with the individual solver routines, so I'm not sure how you
should pass the variables, but perhaps you can start by reading the
docstring (help(solve_linear_system)) where you will see that you
should be passing an augmented system. I don't think you are doing
that.
/c
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