@Stefan You are right. The therms of the expressions have to be combined as much as possible. This is more a pre evaluation as a simplification. Some variables are changing during the repeating calculation of the expressions afterwards. This variables are numpy arrays or normal floats and therfore must be preserved in the expression. I have looked in many python libraries but sympy simplification did what I want. Unfortunatly the syntax dont supports the array style of variables and symbols. The task you suggest with lambdify has to follow after the simplification. Because even with lambdify you have to carry out much more operations than necessary.
Am Freitag, 6. September 2013 01:49:31 UTC+2 schrieb Aaron Meurer: > > As I suggested on the StackOverflow question, you might try using the > matrix expressions. > > Aaron Meurer > > > On Thu, Sep 5, 2013 at 2:53 PM, Stefan Krastanov > <[email protected]<javascript:> > > wrote: > >> Is there a reason not to use Symbols? From your explanations I do not see >> one. If your issue is how to couple the result to something like numpy, >> checkout `lambdify`. >> >> >> On 5 September 2013 15:54, david <[email protected]<javascript:> >> > wrote: >> >>> For better explanation I have done the simplification in MatCad where >>> unassigned variables are seen as symbols in sympy. >>> >>> >>> <https://lh4.googleusercontent.com/-uq82CF7JYZw/UijhDNbjPvI/AAAAAAAAAAM/bPAnd8PQSpI/s1600/simplify+with++arrays.tiff> >>> >>> >>> Am Donnerstag, 5. September 2013 15:19:14 UTC+2 schrieb david: >>> >>>> I have explored the sympy features and i was very impressed with both >>>> the amount of features and the ease of testing with the doc and the >>>> coupled >>>> Live Shell. >>>> I want to write a programm that simplifies expressions as much as >>>> possible to minimize calculation time because they will later be >>>> numericaly >>>> evaluated very often. >>>> The most features I need work very well. But with arrays I have a >>>> problem. >>>> I need to define an array object as an symbol, so that the following is >>>> possible: >>>> >>>> simplify(2.0*2.0*t[0]) >>>> is simplified to: >>>> 4.0*t[0] >>>> >>>> and: >>>> idx = 2 >>>> simplify(2.0*2.0*t[idx]) >>>> shold be simplified to: >>>> 4.0*t[2] >>>> >>>> Is there any way to do this? >>>> >>>> david >>>> >>> >>> -- 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. For more options, visit https://groups.google.com/groups/opt_out.
