Re: [sympy] New to sympy,open source
Hey Devendra, Go through this document to see how to get involved: https://github.com/sympy/sympy/wiki/introduction-to-contributing To learn about GitHub and Git, start with this https://try.github.io/levels/1/challenges/1 Regards Sudhanshu Mishra www.sudhanshumishra.in On Thu, Dec 4, 2014 at 12:53 PM, Devendra Bendkhale deven1028...@gmail.com wrote: Hi I am new to sympy .I study Computer Science and Engineering in Indian Institue of Technology,Guwahati. I like python and maths. Also I liked concept of symbolic mathematics of sympy. I want to contribute to sympy. After reading some posts and articles I came to know that github is used to merge code in sympy . I have never used it before . Please could anyone help me in getting started. Thanks!! -- 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+unsubscr...@googlegroups.com. To post to this group, send email to sympy@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/774ef61a-ed35-41aa-9261-2f5ed70a4343%40googlegroups.com https://groups.google.com/d/msgid/sympy/774ef61a-ed35-41aa-9261-2f5ed70a4343%40googlegroups.com?utm_medium=emailutm_source=footer . 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+unsubscr...@googlegroups.com. To post to this group, send email to sympy@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/CAFW_KCSsdGMuhEtzM1nQvy%2BKR-B%2B1QoW57q955nXsVhjnRiKpA%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
[sympy] Re: problem in solving inequations
On Thursday, December 4, 2014 7:23:28 AM UTC+1, Chris Smith wrote:
Could you do `print filldedent(R);print filldedent(L)` so I can see what
the expressions are that you are trying to solve?
Sorry my list L of 4 relationals was latter renamed R... Here they are
(btw I was not able to use filldedent, using from sympy import * so
I used print(R) and reformat with my editor to have an element per line)
:
R = [(-k**8 + 8*k**6 - 8*k**4 - 16*k**2 - 64)/(k*(k**8 - 2*k**6 - 4*k**4
- 16*k**2 + 8)) 0,
(-k**8 + 8*k**6 - 8*k**4 - 16*k**2 - 64)/(k*(k**8 - 2*k**6 - 4*k**4 -
16*k**2 + 8)) 0,
(k**8 - 6*k**6 + 8*k**2 + 96)/(k*(k**8 - 2*k**6 - 4*k**4 - 16*k**2 +
8)) = 0,
(k**8 - 2*k**7 + 4*k**6 + 4*k**5 - 16*k**4 + 8*k**3 - 40*k**2 + 24*k -
64)/(k*(k**8 - 2*k**6 - 4*k**4 - 16*k**2 + 8)) = 0]
The symbol k is restricted to be real and in (2,3].
(k is introduced with k = symbols('k',real=True,positive=True)).
In fact even if I try to solve for only the first relational I meet the
same error message :
res= solve([k2, k = 3, R[0]],k)
Traceback (most recent call last):
File stdin, line 1, in module
File /usr/lib/python2.7/site-packages/sympy/solvers/solvers.py, line 674,
in solve
symbols=symbols)
File /usr/lib/python2.7/site-packages/sympy/solvers/inequalities.py, line
434, in reduce_inequalities
poly_reduced.append(reduce_rational_inequalities([exprs], gen, assume))
File /usr/lib/python2.7/site-packages/sympy/solvers/inequalities.py, line
209, in reduce_rational_inequalities
solution = solve_rational_inequalities(eqs)
File /usr/lib/python2.7/site-packages/sympy/solvers/inequalities.py, line
144, in solve_rational_inequalities
global_interval -= denom_interval
File /usr/lib/python2.7/site-packages/sympy/core/sets.py, line 250, in
__sub__
return self.intersect(other.complement)
File /usr/lib/python2.7/site-packages/sympy/core/sets.py, line 133, in
complement
return self._complement
File /usr/lib/python2.7/site-packages/sympy/core/sets.py, line 1229, in
_complement
% self)
ValueError: {RootOf(k**8 - 2*k**6 - 4*k**4 - 16*k**2 + 8, 0)}: Complement
not defined for symbolic inputs
Bruno
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[sympy] Re: problem in solving inequations
Oups I just saw that my first and second relationals are the same. So I have to solve for only 3 relationals. I just went to try the wolfram alpha online calculator, I got : 1/ for the first relational : solve((-k**8 + 8*k**6 - 8*k**4 - 16*k**2 - 64)/(k*(k**8 - 2*k**6 - 4*k**4 - 16*k**2 + 8)) 0, k 2, k = 3) alpha gives: 2ksqrt(2/3 (2+(53-3 sqrt(201))^(1/3)+(53+3 sqrt(201))^(1/3))) 2/ for the third one: solve((k**8 - 6*k**6 + 8*k**2 + 96)/(k*(k**8 - 2*k**6 - 4*k**4 - 16*k**2 + 8)) = 0, k 2, k = 3) alpha gives: sqrt(2/3+1/3 (404-36 sqrt(109))^(1/3)+1/3 2^(2/3) (101+9 sqrt(109))^(1/3))=k=3 3/ and for the fourth one: solve((k**8 - 2*k**7 + 4*k**6 + 4*k**5 - 16*k**4 + 8*k**3 - 40*k**2 + 24*k - 64)/(k*(k**8 - 2*k**6 - 4*k**4 - 16*k**2 + 8)) = 0, k 2, k = 3) alpha gives: 2k=3 Bruno -- 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+unsubscr...@googlegroups.com. To post to this group, send email to sympy@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/004501b1-b4a1-416d-acc4-862329a485c4%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[sympy] Sympy assumptions
Suppose that I have an expression e = x**2+sqrt(a**2*b**2) What is the best way to assign to expression assumption that all variables are Positive, so that equivalent of e is x**2+ab? -- 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+unsubscr...@googlegroups.com. To post to this group, send email to sympy@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/d06b2195-1c60-4317-9d19-4909d10c2e30%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [sympy] Sympy assumptions
On Thu, Dec 4, 2014 at 7:38 AM, Paul Royik distantjob...@gmail.com wrote: Suppose that I have an expression e = x**2+sqrt(a**2*b**2) What is the best way to assign to expression assumption that all variables are Positive, so that equivalent of e is x**2+ab? It should be done like this: In [11]: refine(e, Q.positive(a) Q.positive(b)) Out[11]: ___ 2 ╱ 2 2 x + ╲╱ a ⋅b But unfortunately that doesn't work. So the only other way is the old way like this: In [12]: a = Symbol(a, positive=True) In [13]: b = Symbol(b, positive=True) In [14]: x**2+sqrt(a**2*b**2) Out[14]: 2 a⋅b + x Ondrej -- 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+unsubscr...@googlegroups.com. To post to this group, send email to sympy@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/CADDwiVALOT_JKL_4RYEJwWvru7seC1o2%2BcR8tTOj02xEkbdKvQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
[sympy] Eigenvalues of a matrix with symbolic coefficients
I'm having some problems getting sympy to compute eigenvalues of a matrix with symbolic coefficients. A trivial example is: In [4]: M = Matrix([[y, 0], [0, z]]) In [5]: M Out[5]: ⎡y 0⎤ ⎢⎥ ⎣0 z⎦ In [6]: M.eigenvals() Out[6]: ⎧ ____ ⎫ ⎪ ╱2╱2⎪ ⎨y z ╲╱ (y - z) y z ╲╱ (y - z) ⎬ ⎪─ + ─ - ─: 1, ─ + ─ + ─: 1⎪ ⎩2 2 2 2 2 2 ⎭ Clearly the eigenvalues should be y and z so something has gone wrong. It seems that perhaps what happens is that the characteristic polynomial is expanded and then not re-factored when finding solutions: In [7]: (M - x*eye(2)) Out[7]: ⎡-x + y0 ⎤ ⎢ ⎥ ⎣ 0 -x + z⎦ In [8]: (M - x*eye(2)).det() Out[8]: 2 x - x⋅y - x⋅z + y⋅z In [9]: solve((M - x*eye(2)).det(), x) Out[9]: ⎡ __ __⎤ ⎢ ╱2 ╱2 ⎥ ⎢y z ╲╱ (y - z)y z ╲╱ (y - z) ⎥ ⎢─ + ─ - ─, ─ + ─ + ─⎥ ⎣2 2 22 2 2 ⎦ In [10]: factor((M - x*eye(2)).det()) Out[10]: (x - y)⋅(x - z) In [11]: solve(factor((M - x*eye(2)).det()), x) Out[11]: [y, z] Presumably det calls expand and I'm not sure why it would want to do that. Also solve has clearly spotted that this is a second order polynomial since we're using the quadratic formula but no attempt at factorisation is made. I guess that without knowing knowing the sign of y - z you can't know whether sqrt((y-z)**2) is y - z or z - y so the quadratic formula cannot be simplified even though the original polynomial could. Is there some way to adjust this behaviour with flags etc.? Or is it just a case where sympy has some room for improvement? Oscar -- 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+unsubscr...@googlegroups.com. To post to this group, send email to sympy@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/CAHVvXxQqEwSOnm0rR3qnfpKBEorgdcMYgVFSjjYL3Rc%2B5K4YeQ%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
Re: [sympy] Sympy assumptions
I know this way, but is there any way to change this after symbol creation? On Thursday, December 4, 2014 6:29:27 PM UTC+2, Ondřej Čertík wrote: On Thu, Dec 4, 2014 at 7:38 AM, Paul Royik distan...@gmail.com javascript: wrote: Suppose that I have an expression e = x**2+sqrt(a**2*b**2) What is the best way to assign to expression assumption that all variables are Positive, so that equivalent of e is x**2+ab? It should be done like this: In [11]: refine(e, Q.positive(a) Q.positive(b)) Out[11]: ___ 2 ╱ 2 2 x + ╲╱ a ⋅b But unfortunately that doesn't work. So the only other way is the old way like this: In [12]: a = Symbol(a, positive=True) In [13]: b = Symbol(b, positive=True) In [14]: x**2+sqrt(a**2*b**2) Out[14]: 2 a⋅b + x Ondrej -- 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+unsubscr...@googlegroups.com. To post to this group, send email to sympy@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/0057f9b0-377e-4409-aee8-d8284e1e0f06%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
Re: [sympy] Eigenvalues of a matrix with symbolic coefficients
On 04/12/14 16:57, Oscar Benjamin wrote: I'm having some problems getting sympy to compute eigenvalues of a matrix with symbolic coefficients. A trivial example is: In [4]: M = Matrix([[y, 0], [0, z]]) In [5]: M Out[5]: ⎡y 0⎤ ⎢⎥ ⎣0 z⎦ In [6]: M.eigenvals() Out[6]: ⎧ ____ ⎫ ⎪ ╱2╱2⎪ ⎨y z ╲╱ (y - z) y z ╲╱ (y - z) ⎬ ⎪─ + ─ - ─: 1, ─ + ─ + ─: 1⎪ ⎩2 2 2 2 2 2 ⎭ I think this has been improved in the dev version after 0.7.6. I remember commenting on an old issue on this which was then recently closed, but I cannot locate at the moment... test on git master? Colin -- 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+unsubscr...@googlegroups.com. To post to this group, send email to sympy@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/54809D92.4010708%40maths.ox.ac.uk. For more options, visit https://groups.google.com/d/optout. signature.asc Description: OpenPGP digital signature
Re: [sympy] Eigenvalues of a matrix with symbolic coefficients
On 4 December 2014 at 17:44, Colin Macdonald macdon...@maths.ox.ac.uk wrote:
In [4]: M = Matrix([[y, 0], [0, z]])
In [5]: M
Out[5]:
⎡y 0⎤
⎢⎥
⎣0 z⎦
In [6]: M.eigenvals()
Out[6]:
⎧ ____ ⎫
⎪ ╱2╱2⎪
⎨y z ╲╱ (y - z) y z ╲╱ (y - z) ⎬
⎪─ + ─ - ─: 1, ─ + ─ + ─: 1⎪
⎩2 2 2 2 2 2 ⎭
I think this has been improved in the dev version after 0.7.6. I
remember commenting on an old issue on this which was then recently
closed, but I cannot locate at the moment... test on git master?
Yes, you're right. git master shows:
In [3]: Matrix([[y, 0], [0, z]]).eigenvals()
Out[3]: {y: 1, z: 1}
And also:
In [8]: (M - x*eye(2)).det()
Out[8]:
2
x - x⋅y - x⋅z + y⋅z
In [9]: solve((M - x*eye(2)).det(), x)
Out[9]: [y, z]
Thanks for that,
Oscar
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[sympy] a bug: intersection of Line3D and plane
Hi there, Using sympy0.7.6.win32, I run the following python script to try to find the intersection of a Line3D and a Plane. The coordinates for Point3D are from my intermediate result. I test the script in python 2.7.8 (Case 1) and python 3.4.2 (Case 2) and got different results. # from sympy import * l2 = Line3D(Point3D(5004459633/5, -891926590718643/1000, 231800966893633/100), Point3D(5004459633/50, -222981647679771/250, 231800966893633/100)) p2 = Plane(Point3D(402775636372767/100, -97224357654973/100, 216793600814789/100), (-9.0087501922, -4.81170658872543e-13, 0.0)) print(p2.is_parallel(l2)) print(p2.intersection(l2) ### Case 1: = Python 2.7.8 (default, Jun 30 2014, 16:03:49) [MSC v.1500 32 bit (Intel)] on win32 Type copyright, credits or license() for more information. RESTART False [Point3D(4, -1, 2)] Case 2: == Python 3.4.2 (v3.4.2:ab2c023a9432, Oct 6 2014, 22:15:05) [MSC v.1600 32 bit (Intel)] on win32 Type copyright, credits or license() for more information. RESTART False [] If it is a bug, where do I know it is fixed? ouyang -- 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+unsubscr...@googlegroups.com. To post to this group, send email to sympy@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/f6dd0753-9904-4152-ba4b-0413a7bc9400%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
