sage: algdep(RealField(20)(1.4142), 2)
x^2 - 2
Note that you have to specify the maximal degree. Be careful about the input
sage: algdep(1.4142, 2)
5000*x - 7071
This is using the PARI/GP algdep command (whose algorithm is a LLL
reduction).
Vincent
On 20/07/2017 16:31, Daniel Krenn wrote:
Dear all,
I vaguely remember a discussion on this list some years ago about the
following: Given a floating point number, what is a good guess for the
simplest possible algebraic number that approximates this?
E.g. The input 1.4142 gives back sqrt(2) or x^2-2 and says that this is
approximates the input on the first four digits. (Of course much more
precise guesses would be possible, but a simple one should just do fine.)
(I am aware that this is not a Sage-specific question, but when I
remember correctly, there was some software mentioned in that thread
years ago, which can do this. Maybe I am completely wrong and it was
somewhere else; but maybe someone has an idea if such a program exists.)
Best wishes
Daniel
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