[Numpy-discussion] Dealing with roundoff error
Mike Sarahan
msarahan@gmail....
Sat Mar 27 18:38:27 CDT 2010
Hi all,
I have run into some roundoff problems trying to line up some
experimental spectra. The x coordinates are given in intervals of 0.1
units. I read the data in from a text file using np.loadtxt().
I think Robert's post here explains why the problem exists:
http://mail.scipy.org/pipermail/numpy-discussion/2007-June/028133.html
However, even linspace shows roundoff error:
a=np.linspace(0.0,10.0,endpoint=False)
b=np.linspace(0.1,10.1,endpoint=False)
np.sum(a[1:]==b[:-1]) # Gives me 72, no 100
What is the best way to deal with it? Multiply the intervals by 10,
then convert them to ints?
Thanks,
Mike
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