[changeset] behavior of sph2cart() doesn't match matlab (?)

[Ben Abbott]

On Jan 16, 2009, at 11:09 AM, Ben Abbott wrote:

>
> On Friday, January 16, 2009, at 10:35AM, "michael tesch" <tesch1 at gmail.com 
> > wrote:
>>
>> On Fri, Jan 16, 2009 at 6:35 AM, Ben Abbott <bpabbott at mac.com> wrote:
>>>
>>> On Jan 15, 2009, at 8:57 PM, michael tesch wrote:
>>>
>>>> GNU Octave, version 3.0.2, on macosx, from 'port'.
>>>>
>>>> I can't actually verify this on the matlab side, but I got code  
>>>> that
>>>> was developed in matlab that did the following:
>>>>
>>>> for nsp=1:sz
>>>>  [TH,PHI]=cart2sph(xx,yy,zz);
>>>>  [X,Y,Z]=sph2cart(TH,PHI,A);
>>>>  spoke=[X ;Y ;Z];
>>>> end
>>>>
>>>> Where xx,yy,zz,TH,PHI were all scalars, and A was a 1xN vector.   
>>>> The
>>>> result was that spoke was a matrix of 3xN.
>>>>
>>>> the Octave implementation of sph2cart() dies with an error about
>>>> mismatched dimensions of parameters.
>>>
>>>>
>>>
>>> I'm unable to reproduce any problem in the developers sources.
>>>
>>> Nothing depends upon "nsp", so why the loop?
>>>
>>> TH, PHI should each have same size as xx, yy, & zz. Are you sure A  
>>> has the
>>> same size?
>>>
>>> To make certain everything is sized/shaped correctly, try  
>>> inserting the line
>>> below after cart2sph
>>>
>>>       whos xx yy zz TH PHI
>>>
>>> Ben
>>>
>>
>> thanks for your answer.
>>
>> sorry, i should have removed the loop from the example snippet.
>> the point is that the code works in matlab, but doesn't work in  
>> octave,
>> because matlab's sph2cart() (apparently) accepts when TH and PHI
>> are scalars and A is a vector, whereas octave's sph2cart() bombs out.
>>
>> xx,yy,zz,TH,PHI are all scalars.  A is a vector (of points along a  
>> line)
>> and spoke should be the cartesian coordinates of the points along  
>> that line.
>>
>> i have a workaround, but read that differences between octave and
>> matlab were considered bugs.
>>
>> mt
>>
>
> Ok, I understand and have confirmed the problem. Also, Matlab's  
> documentation confirms their behavior is intended.
>
> I don't have time to look at the details at the moment. There are  
> related functions that will need to be modified as well. I'll try to  
> get to this tonight or over the weekend.
>
> Ben

Changeset attached.  While permitting coordinates to be scalars, I  
also took the liberty to change the variables to be all lower case.

In addition, the doc-strings have been changed and tests have been  
added.

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