Okay. Thanks again for your help. On Thursday, 5 November 2015 00:36:46 UTC+8, Aaron Meurer wrote: > > Yes, for now, Mul automatically distributes constants, so you have to > use evaluate=False to factor out something like -1. > > Aaron Meurer > > On Wed, Nov 4, 2015 at 5:13 AM, Hugh <714...@gmail.com <javascript:>> > wrote: > > Thanks Aaron for pointing out the simplification section of the > tutorial. > > > > Actually, collect(expr1, [x11, x12, x13]) does almost what I wanted. I > > still need to factor a -1 from x12( -x21x33 + x23x31). How would you do > it > > using replace() like what I did? I also tried putting (x12*a).factor() > as > > the value for replace but that didn't work. I had to use Mul() with > evaluate > > = False to get it to do what I wanted. > > > > On Wednesday, 4 November 2015 06:19:34 UTC+8, Aaron Meurer wrote: > >> > >> A good start would be the simplification section of the tutorial > >> http://docs.sympy.org/latest/tutorial/index.html. > >> > >> In this case, collect(expr1, [x11, x12, x13]) does what you want. > >> factor() only does complete factorizations (into products of terms). > >> This is explained in more depth in the tutorial. > >> > >> Aaron Meurer > >> > >> On Tue, Nov 3, 2015 at 2:47 PM, Hugh <714...@gmail.com> wrote: > >> > import sympy > >> > sympy.init_session() > >> > > >> > > >> > x11, x12, x13, x21, x22, x23, x31, x32, x33 = symbols('x_1:4(1:4)') > >> > > >> > A = Matrix(3,3,symbols('x_1:4(1:4)')) > >> > expr1 = A.det() > >> > > >> > expr2 = x11*(x22*x33 - x23*x32) - x12*(x21*x33 -x23*x31) + > x13*(x21*x32 > >> > - > >> > x22*x31) > >> > > >> > # How to get expr2 from expr1? > >> > > >> > I would like to use sympy to rewrite expressions just like how people > >> > would > >> > commonly do when writing proofs or doing homework. What are the > >> > documentation that I must read so that I can be proficient at this? > >> > > >> > I've read the tutorial and some of the modules in the module > reference > >> > but > >> > feel that I have just barely touched the surface of sympy's > >> > capabilities. > >> > For example, in the above code snippet, I don't know how to > manipulate > >> > expr1 > >> > to get expr2. I thought expr1.factor() would work but it didn't. > >> > > >> > Please advise. > >> > > >> > -- > >> > 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 sympy+un...@googlegroups.com. > >> > To post to this group, send email to sy...@googlegroups.com. > >> > 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/9cbb1995-3987-44f1-8c72-6de11e6a4013%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 sympy+un...@googlegroups.com <javascript:>. > > To post to this group, send email to sy...@googlegroups.com > <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/438ac161-214e-497d-964c-87900be74dcb%40googlegroups.com. > > > > > > For more options, visit https://groups.google.com/d/optout. >
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