[Numpy-discussion] numpy.correlate with phase offset 1D data series

Ray Schumacher subscriber100@rjs....
Tue Mar 4 13:10:54 CST 2008


At 03:28 PM 3/3/2008, Ann wrote:
> >Sounds familiar. If you have a good signal-to-noise ratio, you can get
> >subpixel accuracy by oversampling the irfft, or better but slower, by
> >using numerical optimization to refine the peak you found with argmax.

the S/N here is poor, and high data rates work against me too...

 > I would be inclined to use convolve (or scipy.ndimage.convolve, which
 > uses a Fourier-domain method), since it is somewhat better specified.

I'll give it a try as well.
I'm guessing scipy.ndimage.correlate1d is a Fourier method too?

 > From: "Timothy Hochberg" <tim.hochberg@ieee.org>
 >
 > I'm going to guess that you are using some flavor of Unix, since I also
 > downloaded using Firefox and the data ends up corrupted. My hypothesis is
 > that Firefox doesn't recognize the mime type and treats it as a text file,
 > corrupting it on Windows, but not on Unix. Then again, maybe you're not
 > using Unix and my installation of Firefox is just broken.

I think that is the case, I have Win2K on this box

 > With the CSV version I do get a peak at the (un)expected location (7489//2).
 > The peak is pretty flat and only twice the size of the surrounding gunk, but
 > it looks more or less legit.

I don't see that in my pylab plot! There's actually a dip, and the 
whole plot is symmetric about 3744
http://rjs.org/Python/corr_array.jpg, self xcorr of
http://rjs.org/Python/data.jpg

I'll be upgrading my install here shortly though to py2.5 and associated libs.
My compiler/distutils environment is broken.

Thanks, Ray 


-- 
No virus found in this outgoing message.
Checked by AVG Free Edition. 
Version: 7.5.516 / Virus Database: 269.21.4/1310 - Release Date: 3/4/2008 8:35 AM




More information about the Numpy-discussion mailing list