Yes! I now remember reading that in the docs a few days ago, but I missed it today. Thanks.
On Wednesday, November 2, 2016 at 2:38:51 PM UTC-5, Aaron Meurer wrote: > In general you should use MatrixSymbol to represent expressions of > matrices. If you do that, substitution should work. > > Aaron Meurer > > On Wed, Nov 2, 2016 at 3:35 PM, Nathan Thern <[email protected] > <javascript:>> wrote: > > In the following session I create several symbolic expressions and > > manipulate them via substitution. > > Why does the last command produce an error? > > > > Jupyter console 5.0.0 > > Python 3.5.2 (v3.5.2:4def2a2901a5, Jun 25 2016, 22:01:18) [MSC v.1900 32 > bit > > (Intel)] > > Type "copyright", "credits" or "license" for more information. > > IPython 5.1.0 -- An enhanced Interactive Python. > > ? -> Introduction and overview of IPython's features. > > %quickref -> Quick reference. > > help -> Python's own help system. > > object? -> Details about 'object', use 'object??' for extra details. > > > > In [1]: import sympy > > In [2]: sympy.__version__ > > Out[2]: '1.0' > > > > In [3]: sympy.var('Xa,Ya,Za,Xb,Yb,Zb,Na,Nb,Sa,Sb') > > Out[3]: (Xa, Ya, Za, Xb, Yb, Zb, Na, Nb, Sa, Sb) > > > > In [4]: Sa=Xa/7 > > In [5]: Sb=Yb**3 > > In [6]: Sa - Sb > > Out[6]: Xa/7 - Yb**3 > > > > In [7]: NEa=sympy.Matrix([[Xa,Ya,Za]]) > > In [8]: NEb=sympy.Matrix([[Xb,Yb,Zb]]) > > In [9]: NEa - NEb > > Out[9]: Matrix([[Xa - Xb, Ya - Yb, Za - Zb]]) > > > > In [10]: V=Na-Nb > > In [11]: V.subs({Na:Sa,Nb:Sb}) > > Out[11]: Xa/7 - Yb**3 > > > > In [12]: V.subs({Na:NEa,Nb:NEb}) > > > --------------------------------------------------------------------------- > > AttributeError Traceback (most recent call > last) > > > > Long Traceback output follows ending with > > > > AttributeError: ImmutableMatrix has no attribute as_coeff_Mul. > > Which I don't understand in any useful way. > > > > What concept am I missing? Are matrices not substitutable? > > > > NT > > > > -- > > 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 https://groups.google.com/group/sympy. > > To view this discussion on the web visit > > > https://groups.google.com/d/msgid/sympy/9aeb7c9c-6747-4746-8d35-eedf3b6bb652%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 https://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/1bdcb8d6-3e35-4758-8c93-27a6a095911b%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
