Re: [Numpy-discussion] largest matrix element
Hi Scott, et al. First off I goofed -- that last reply should have gone to the list as a whole. Second, mere seconds after I pushed send I realized one problem with it: 'flat' only works for contiguous arrays. Its probably safer to use ravel after all, unless it's known that the array is contiguous. On the other hand, it would be slightly more efficient to ravel the matrix after taking its absolute value since ravel potentially allocates a new array and an array of Floats is going to be half the size of an array of Complexes. But then we know the resulting array is going to be contiguous. So after rewriting and erasing the thing a few times I end up with: max(abs(a).flat) Which is almost the same as my first one, except that the flat has been moved and now it should work when the array starts out noncontiguous. -tim
Hi Tim,
Looks good to me! ;)
Scott
Tim Hochberg wrote:
----- Original Message ----- From: "Scott Ransom"
Cc: ; Sent: Tuesday, July 24, 2001 12:24 PM Subject: Re: [Numpy-discussion] largest matrix element Charles G Waldman wrote:
nils.wagner@freenet.de writes:
Given a complex Matrix A(m,n) How can I get the absolute value of the largest matrix element very efficiently ?
How about
sqrt(max((asarray(A)*conjugate(asarray(A))).real))
I if you want the global maximum you need a ravel in there:
sqrt(max(ravel((asarray(a)*conjugate(asarray(a))).real)))
I must be missing something. What's wrong with:
max(abs(a.flat)) ?
-tim
-- Scott M. Ransom Address: Harvard-Smithsonian CfA Phone: (617) 496-7908 60 Garden St. MS 10 email: ransom@cfa.harvard.edu Cambridge, MA 02138 GPG Fingerprint: 06A9 9553 78BE 16DB 407B FFCA 9BFA B6FF FFD3 2989
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Tim Hochberg