[Numpy-discussion] Testing for close to zero?

Jonathan Taylor jonathan.taylor@utoronto...
Mon Jan 19 14:43:55 CST 2009


Hi,

When solving a quadratic equation I get that alpha =
-3.78336776728e-31 which I believe to be far below machine precision:

finfo(float).eps
2.2204460492503131e-16

But an if statement like:

if alpha == 0:
   ...

does not catch this.  Is there a better way to check for things that
are essentially zero or should I really be using

if np.abs(alpha) < finfo(float).eps:
   ...

?

Thanks for any help.
Jonathan.


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