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A combination of commands partial_fraction(x) and coefficient(x,n)

asked 2013-04-12 12:00:11 -0500

k1 gravatar image

I have asked this question over here but I got no answer.

I am trying to do some iterative calculations where each time SAGE constructs a fraction and lists the coefficients in the partial fraction decomposition of that fraction. I realized that doing everything symbolically, SAGE wants to keep everything as integer as possible. So what it does is to simplify fractions like 1/(x-3/2) as 2/(2x-3) and then when I ask for

f.coefficient(x-3/2,-1)

it returns 0, while I expect it to return 1.

I have tried to solve things numerically, but there are two problems:

  1. The errors get really big after each iteration
  2. It takes much much longer to calculate it

Any suggestions to get SAGE to solve this is greatly appreciated.

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answered 2013-04-12 17:30:23 -0500

ppurka gravatar image

You can do something like this

sage: f = 1/(x-3/2)
sage: g = f.denominator()
sage: f.coeff(f.denominator(), -1) / g.leading_coeff(x)
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Thanks, but the problem is that after partial fraction decomposition I have a bunch of fractions added to each other.

k1 gravatar imagek1 ( 2013-04-16 04:22:06 -0500 )edit

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Asked: 2013-04-12 12:00:11 -0500

Seen: 125 times

Last updated: Apr 12 '13