Status: Accepted
Owner:
Labels: Type-Defect Priority-Medium Series
New issue 3135 by someb...@bluewin.ch: Multiple series expansions
http://code.google.com/p/sympy/issues/detail?id=3135
Multiple series expansions in a row wrt different variables do not work.
Let me show a simple example:
Comment #1 on issue 3135 by asmeu...@gmail.com: Multiple series expansions
http://code.google.com/p/sympy/issues/detail?id=3135
I think the first order term has to keep track of the other variables. So
the correct order should be something like O(exp(y)*x**6), not just
O(x**6). Are our mul
Comment #3 on issue 3135 by avichal@gmail.com: Multiple series
expansions
http://code.google.com/p/sympy/issues/detail?id=3135
Since multivariate cases can be handled by Order, I tried the following
example
In [3]: Order(x**6*exp(y))
Out[3]:
⎛ 6 ⎞
O⎝x ; (x, y) → (0, 0
Comment #4 on issue 3135 by skirpic...@gmail.com: Multiple series expansions
http://code.google.com/p/sympy/issues/detail?id=3135
It gives only x**6 instead of x**6*exp(y)? Is it a bug or is this
expected?
Of course, it's expected:
http://en.wikipedia.org/wiki/Big_O_notation#Multiple_variabl
Comment #5 on issue 3135 by avichal@gmail.com: Multiple series
expansions
http://code.google.com/p/sympy/issues/detail?id=3135
Of course, it's expected
Then I didn't understand what is meant by the below statement?
So the correct order should be something like O(exp(y)*x**6), not just
Comment #6 on issue 3135 by avichal@gmail.com: Multiple series
expansions
http://code.google.com/p/sympy/issues/detail?id=3135
Multivariate order is a bit unclear to me.
I did read the Wikipedia article and I guess the following is causing the
bug.
In the given example I expect the Or
Comment #7 on issue 3135 by skirpic...@gmail.com: Multiple series expansions
http://code.google.com/p/sympy/issues/detail?id=3135
I guess the following is causing the bug.
Please check first "the following".
In the given example I expect the Order term is:-
Order(y**6*x**5 + y**6*x**4 + ...
Comment #8 on issue 3135 by avichal@gmail.com: Multiple series
expansions
http://code.google.com/p/sympy/issues/detail?id=3135
However is it expected to simplify to Order(y**6*x**5)
The output will change if we assume that x->oo and y->oo, right?
In [18]: Order(y**6*x**5 + y**6*x**4, (
Comment #9 on issue 3135 by asmeu...@gmail.com: Multiple series expansions
http://code.google.com/p/sympy/issues/detail?id=3135
The O that you know from computer science is order at infinity. The O used
in series is order at 0. You can think of the two as basically opposite.
For order at inf
Comment #10 on issue 3135 by skirpic...@gmail.com: Multiple series
expansions
http://code.google.com/p/sympy/issues/detail?id=3135
The output will change if we assume that x->oo and y->oo, right?
Yes, in this case.
So when doing series, is it assumed that both are tending to 0?
Yes.
A
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