Yes a typo. Dyslexia doesn't always come in handy. I think that using jacobian is the elegant solution. The not evaluating the diff is essentially only an issue when I wanted to texify the intermediate results of a derivation and compare with the original publication. Now everything works and after lambdify my script works like a charm. Thanks, Janwillem
On May 4, 4:47 pm, b45ch1 <sebastian.wal...@gmail.com> wrote: > May I ask in what context you require the matrix derivatives. > Depending on what you are after an Algorithmic Differentiation (AD) > tool could also be a viable alternative. > > With an AD tool you could differentiate functions (i.e. compute > gradient, Jacobian, Hessian, higher order tensors) very easily and > efficiently. > > An example of what functions are possible: > > def f(A,x): > for n in range(30): > y = dot(x.T,dot(A,x)) > A = inv(A) - dot(x,x.T) * y > > return trace(A) > > best regards, > Sebastian > > On May 4, 10:32 am, janwillem <jwevand...@xs4all.nl> wrote: > > > > > I need some explanation on the workings of SymPy. As an example the > > following script: > > import sympy > > X, F, B = sympy.symbols('XFB') > > Y = X / F - B #eqn 1 > > DY = sympy.Matrix(sympy.diff(Y, (X, F, B))).T > > print DY > > > I had expected (eqn 2): [1/F, -X/F**2, -1] > > But get: [D(-B + X/F, X), D(-B + X/F, F), D(-B + X/F, B)] > > > Not after doing a trick of which I cannot remember why I tried it, I > > get the desired result > > DY = DY.subs({X:X, F:F, B:B}) > > From the doc I had thought that DY.doin() would work but that gives > > "raise AttributeError()". > > So there is obviously something I do not understand, please some help > > Janwillem > > > -- > > You received this message because you are subscribed to the Google Groups > > "sympy" group. > > To post to this group, send email to sy...@googlegroups.com. > > To unsubscribe from this group, send email to > > sympy+unsubscr...@googlegroups.com. > > For more options, visit this group > > athttp://groups.google.com/group/sympy?hl=en. > > -- > You received this message because you are subscribed to the Google Groups > "sympy" group. > To post to this group, send email to sy...@googlegroups.com. > To unsubscribe from this group, send email to > sympy+unsubscr...@googlegroups.com. > For more options, visit this group > athttp://groups.google.com/group/sympy?hl=en. -- You received this message because you are subscribed to the Google Groups "sympy" group. To post to this group, send email to sy...@googlegroups.com. To unsubscribe from this group, send email to sympy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.