Hi all- Interested party just wondering if there is any update on this.
Cheers, Adam On Tuesday, June 24, 2014 at 10:01:56 AM UTC-7, Aaron Meurer wrote: > > A multidimensional version of collect() would probably be the best > abstraction. > > Aaron Meurer > > On Sun, Jun 15, 2014 at 10:26 AM, James Crist <[email protected] > <javascript:>> wrote: > > We certainly could. The question would then be what the scope of the > method > > should be. Should it only handle systems that can be expressed as Ax = > b? Or > > should it behave like `CoefficientArrays` mentioned above, and handle Ax > + > > Bx^2 + Cx^3 + D = 0? Either way, I think it should error if the form > can't > > be matched exactly (i.e. don't linearize, just express a linear, or > > polynomial, system as matrices). > > > > > > On Saturday, June 14, 2014 6:44:21 PM UTC-5, Aaron Meurer wrote: > >> > >> Oh, of course. B is on the rhs. This is probably more natural to me > too. > >> > >> Should we make a convenience function that does this? I think this use > >> of jacobian would be lost on most people. > >> > >> Aaron Meurer > >> > >> On Sat, Jun 14, 2014 at 6:29 PM, James Crist <[email protected]> wrote: > >> > It's just the convention I'm most used to. Systems that can be > expressed > >> > as > >> > A*x = B I usually solve for x, or if A isn't square, the least > squares > >> > solution x. In both cases you need A and B in this form. I suppose Ax > + > >> > B > >> > could seem more natural though. > >> > > >> > On Friday, June 13, 2014 6:45:48 PM UTC-5, Aaron Meurer wrote: > >> >> > >> >> That's a clever trick. I should have thought of that. > >> >> > >> >> Is there any reason you let system = A*x - B instead of A*x + B? The > >> >> latter seems more natural. > >> >> > >> >> Aaron Meurer > >> >> > >> >> On Sat, Jun 7, 2014 at 12:28 AM, James Crist <[email protected]> > wrote: > >> >> > I just answered this on gitter earlier today, but you can just > take > >> >> > the > >> >> > jacobian of the system to get its matrix form. For example: > >> >> > > >> >> > In [1]: from sympy import * > >> >> > > >> >> > In [2]: a, b, c, d = symbols('a, b, c, d') > >> >> > > >> >> > In [3]: x1, x2, x3, x4 = symbols('x1:5') > >> >> > > >> >> > In [4]: x = Matrix([x1, x2, x3, x4]) > >> >> > > >> >> > In [5]: system = Matrix([a*x1 + b*x2 + c, > >> >> > ...: c*x1 + d*x3 + 2, > >> >> > ...: c*x3 + b*x4 + a]) > >> >> > > >> >> > In [6]: A = system.jacobian(x) > >> >> > > >> >> > In [7]: B = A*x - system > >> >> > > >> >> > In [8]: A > >> >> > Out[8]: > >> >> > Matrix([ > >> >> > [a, b, 0, 0], > >> >> > [c, 0, d, 0], > >> >> > [0, 0, c, b]]) > >> >> > > >> >> > In [9]: B > >> >> > Out[9]: > >> >> > Matrix([ > >> >> > [-c], > >> >> > [-2], > >> >> > [-a]]) > >> >> > > >> >> > In [10]: assert A*x - B == system > >> >> > > >> >> > The functionality I'm adding for my GSoC for linearizing a system > of > >> >> > equations will also be able to return these matrices in a > convenient > >> >> > form. > >> >> > But it's not terribly difficult to solve for these arrangements > using > >> >> > the > >> >> > current functionality. > >> >> > > >> >> > > >> >> > > >> >> > > >> >> > > >> >> > > >> >> > > >> >> > On Thursday, June 5, 2014 4:22:52 PM UTC-5, Andrei Berceanu wrote: > >> >> >> > >> >> >> Was this implemented into sympy at any point? It could be the > >> >> >> equivalent > >> >> >> of Mathematica's CoefficientArrays function. > >> >> >> > >> >> >> On Thursday, November 14, 2013 5:56:22 AM UTC+1, Chris Smith > wrote: > >> >> >>> > >> >> >>> I forgot that as_independent, without the as_Add=True flag will > >> >> >>> treat > >> >> >>> Muls differently. The following will be more robust: > >> >> >>> > >> >> >>> def eqs2matrix(eqs, syms, augment=False): > >> >> >>> """ > >> >> >>> >>> s > >> >> >>> [x + 2*y == 4, 2*c + y/2 == 0] > >> >> >>> >>> eqs2matrix(s, (x, c)) > >> >> >>> (Matrix([ > >> >> >>> [1, 0], > >> >> >>> [0, 2]]), Matrix([ > >> >> >>> [-2*y + 4], > >> >> >>> [ -y/2]])) > >> >> >>> >>> eqs2matrix([2*c*(x+y)-4],(x, y)) > >> >> >>> (Matrix([[2*c, 2*c]]), Matrix([[4]])) > >> >> >>> """ > >> >> >>> s = Matrix([si.lhs - si.rhs if isinstance(si, Equality) else > si > >> >> >>> for > >> >> >>> si in eqs]) > >> >> >>> sym = syms > >> >> >>> j = s.jacobian(sym) > >> >> >>> rhs = -(s - j*Matrix(sym)) > >> >> >>> rhs.simplify() > >> >> >>> if augment: > >> >> >>> j.col_insert(0, rhs) > >> >> >>> else: > >> >> >>> j = (j, rhs) > >> >> >>> return j > >> >> >>> > >> >> > -- > >> >> > You received this message because you are subscribed to the Google > >> >> > Groups > >> >> > "sympy" group. > >> >> > To unsubscribe from this group and stop receiving emails from it, > >> >> > send > >> >> > an > >> >> > email to [email protected]. > >> >> > To post to this group, send email to [email protected]. > >> >> > Visit this group at http://groups.google.com/group/sympy. > >> >> > To view this discussion on the web visit > >> >> > > >> >> > > >> >> > > https://groups.google.com/d/msgid/sympy/8fb2dae4-9f46-4c1b-b96f-83033278c27d%40googlegroups.com. > > > >> >> > > >> >> > For more options, visit https://groups.google.com/d/optout. > >> > > >> > -- > >> > You received this message because you are subscribed to the Google > >> > Groups > >> > "sympy" group. > >> > To unsubscribe from this group and stop receiving emails from it, > send > >> > an > >> > email to [email protected]. > >> > To post to this group, send email to [email protected]. > >> > Visit this group at http://groups.google.com/group/sympy. > >> > To view this discussion on the web visit > >> > > >> > > https://groups.google.com/d/msgid/sympy/a9c5f7ba-1c2d-4673-a8d4-b1253c150054%40googlegroups.com. > > > >> > > >> > For more options, visit https://groups.google.com/d/optout. > > > > -- > > You received this message because you are subscribed to the Google > Groups > > "sympy" group. > > To unsubscribe from this group and stop receiving emails from it, send > an > > email to [email protected] <javascript:>. > > To post to this group, send email to [email protected] > <javascript:>. > > Visit this group at http://groups.google.com/group/sympy. > > To view this discussion on the web visit > > > https://groups.google.com/d/msgid/sympy/0b486c56-8a2b-48a5-a210-f49b6d39899f%40googlegroups.com. > > > > > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sympy" group. 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