On Tuesday, January 14, 2014 11:04:45 PM UTC-5, Alasdair wrote:
>
> I think this was asked a few years ago... anyway, I'm doing some
> computations for which Maxima's "tellrat(X)", which basically means
> substitute 0 for X wherever it occurs in a rational expression, is useful,
> It stops expressions growing huge by simply and automatically making vast
> unnecessary chunks of them zero. However, if I want to do this in Sage I
> either have to start a Maxima sub-shell, or use maxima("do this"), or
> maxima.do_this(), and move expressions to and fro between Sage and Maxima.
> This is all do-able, but also a pain. Is there any way of limiting
> expressions in Sage (for example an expansion of nested Taylor polynomials)
> by automatically making all powers above a certain value zero?
>
Is it possible for you to use `expression.maxima_methods().tellrat` for
this? I haven't tried it, but sometimes this is useful. For this which
require inputs, I have had varying degrees of success passing them.
As for power series, I am pretty sure that you could use truncated power
series of a certain degree and all higher powers would show up as O(x^5) or
something like that.
Sorry for the brevity of this reply, I hope it does prove helpful
nonetheless.
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