On Mon, Oct 4, 2010 at 5:40 PM, Scott <spectre...@gmail.com> wrote:
> Hello. I some very large polynomials. Some coefficients are very
> small (E-16) and I'd like to get rid of these terms. I found a
> previous method with a solution posted here:
> <http://groups.google.com/group/sympy/browse_thread/thread/
> e244e9d9431f3acd/add6f883e7419b27?lnk=gst&q=close+to
> +zero#add6f883e7419b27>
> def chop(expr, tol=1e-6):
> return Add(term for term in expr.as_Add() if term.as_coeff_terms()
> [0] >= tol)
>
> However, when I try this method, it doesn't seem to work. I have the
> latest sympy (0.6.7). The error demonstrated below is the same as the
> one I get using that chop function. I'm running this on Windows, but
> could try it on Linux of it would make a difference (though ultimately
> I need a method that works on both).
>
>>>> type(x+y)
> <class 'sympy.core.add.Add'>
>>>> (x+y).as_Add()
> Traceback (most recent call last):
> File "(stdin)", line 1, in <module>
> AttributeError: 'Add' object has no attribute 'as_Add'
Since you have a large polynomial, you can do something like this:
def chop(expr, tol=1e-6):
if isinstance(expr, Add)
return Add(term for term in expr.args if
term.as_coeff_terms()[0] >= tol)
else:
raise NotImplementedError()
Ondrej
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