[Numpy-discussion] Re: [SciPy-user] Fast Gauss Transform
Travis Oliphant
oliphant.travis at ieee.org
Wed Mar 22 09:45:59 CST 2006
David Huard wrote:
> While fiddling with new code to compute kde, I noticed that
> gaussian_kde has an unexpected behavior for 1D arrays.
>
> For instance :
>
> x = rand(1000)
> g = gaussian_kde(x)
> g(z)
>
> returns the same value no matter what z is. The problem disappears for
> multidimensional data. The dot product (self.inv_cov, diff) seems to
> be causing the problem, doing the product only for the first element
> of diff and returning zeros for the rest. I guess this is not the
> intended behavior for dot.
Yet another untested branch of the optimized dot code. Apparently it's
been very hard to get this one right after re-writing the
scalar-multiplication portion. Scalar multiplication is used in several
branches but the parameters must be set just right.
You were exposing a (1,1) x (1,N) error that uses BLAS scalar
multiplication at the core but the number of multiplies was set to 1
rather than N.
I added a test for this case in numpy and fixed the problem. Thanks
for the report.
-Travis
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