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[Octave-bug-tracker] [bug #40813] atan2 returns no results for sparse ma

From: Stefan Mahr
Subject: [Octave-bug-tracker] [bug #40813] atan2 returns no results for sparse matrices
Date: Mon, 20 Jan 2014 16:54:57 +0000
User-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Ubuntu Chromium/31.0.1650.63 Chrome/31.0.1650.63 Safari/537.36

Follow-up Comment #1, bug #40813 (project octave):

Attached a possible fix. Don't know if 'copy_or_memcopy' is ok here, but seems
the be the fastest solution.

One option would be to copy the whole sparse matrix using existing method, but
then data is copied for nothing. Other possibility is to rewrite column and
row index within for loop, but this is slow. Third option: Create new method?

Also, MATLABs behaviour differs a little bit. This is also fixed with the
attached patch.

This is the MATLAB result:

>>     x=sparse([1 2]);   
>>     atan2(x,x)
ans =
   (1,1)            0.785398163397448
   (1,2)            0.785398163397448
>>     atan2(x,2)
ans =
   (1,1)            0.463647609000806
   (1,2)            0.785398163397448
>>     atan2(x,[1 2])
ans =
   (1,1)            0.785398163397448
   (1,2)            0.785398163397448
>>     atan2(2,x)
ans =
          1.10714871779409         0.785398163397448
>>     atan2([1 2],x)
ans =
         0.785398163397448         0.785398163397448

(file #30320)

Additional Item Attachment:

File name: atan2_spare.patch              Size:1 KB


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