I suppose that to do what you want one must fix http://code.google.com/p/sympy/issues/detail?id=2759 as Aaron said.
On 10 January 2012 10:57, [email protected] < [email protected]> wrote: > > > On 10 January 2012 10:26, John B <[email protected]> wrote: > >> On Jan 9, 6:42 am, Matthew <[email protected]> wrote: >> > You could do the above by explicitly making a scalar symbol for each >> > of x[0], x[1], ... >> > >> Hello Matthew. I realize I could use a scalar for each x[i], but I >> was looking for a way to use only the vector symbol x[i]. It makes >> the results of differentiation much more tidy, especially when f has >> many terms. You can do this in Mathematica and it is a nice feature. >> In my example, f = Sum(5*x[i]**2, (i,0,n)), x[i] is a vector. In >> Mathematica you can also symbolically differentiate with matrices. >> For example, you can take the derivative of f = Sum(5*x[i,j]**2, (i, >> 0,n)) and obtain the symbolic result: >> df/dx = Sum(10*x[i,j], (i,0,n)) >> > I don't understand that last result. I looked up the definition of matrix > derivative in wikipedia but the article is disputed and the definition is > not complete. Could you show me some resource where the definition and > usecases are shown? > > Back to your question. I don't think there is a direct way to do this with > sympy at the moment. But... > > There is DeferredVector that with some work can be extended to do this. > But I don't think that the idea behind it was to do that. (The others > should correct me if I'm wrong) > > On the other hand there was the demand for a MatrixSymbol class. I suppose > that is the way to do what you want but this is not yet implemented. If you > think that it covers what you want to do you may add to the discussion on > the wiki page https://github.com/sympy/sympy/wiki/Matrix-Expressions > > I also saw that the tensor analysis is supposed to do the same thing > (according to wikipedia). There is a tensor module (but it's actually just > objects with index, not real tensors (please correct me if I'm wrong on > this)). It seems to me it's used mainly for code generation so I'm not sure > if it's the best tool for this problem. Finally there is the GA module that > is frequently mentioned in this type of discussions. But the formalism > presented by it is quite different even if it is equivalent. > > >> John >> >> -- >> You received this message because you are subscribed to the Google Groups >> "sympy" group. >> To post to this group, send email to [email protected]. >> To unsubscribe from this group, send email to >> [email protected]. >> For more options, visit this group at >> http://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 [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/sympy?hl=en.
