Re: [Rtftr-devel] some ray of hope after using vigra

[Abhishek D. <the...@gm...>]

Hi Anjan,
Vigra has option to get different types of views of a matrix (column view,
row view, etc). After obtaining a particular view, you can use the sort
method. I don't have the details.

The best option I see is that you store your matrix in a vector< vector<int>
> STL container and use the STL sort algorithm to sort each column.
eg:

// NOTE: you have to create 6 rows of 15000 length records as you want to
sort each column
vector < vector <int> > mydata(6, vector<int>(15000) )

vector < vector <int> >::iterator v_itr;
for( v_itr = mydata.begin(); v_itr != mydata.end(); v_itr++)
{
      sort( *v_itr.begin(), *v_itr.end() );
}
// now everything in mydata is sorted column wise

hope this helps

bye

On Sat, Dec 20, 2008 at 9:59 PM, Anjan <roc...@gm...> wrote:

> Hi,
> In adaboost implementation in C++, i need to process a very large matrix,
> around size of 15000x6. I think OpenCV's cvMat can be used to store it. But,
> I need to sort the matrix according to one of the columns. Do you guys have
> any idea if opencv, vigra, octave etc has this function? I'm trying to avoid
> doing this myself.
> On Sat, Dec 20, 2008 at 9:29 PM, lakesh <lak...@gm...> wrote:
>
>> Hi Abhishek,
>> I think you deleted the matlab and kepenekci_part2 directories during your
>> previous commits. I am adding them again ok.
>>
>>
>> On Sat, Dec 20, 2008 at 9:19 PM, lakesh <lak...@gm...>wrote:
>>
>>> Also about sigma most of the papers they have taken 2pi like us. But this
>>> is totally arbitrary as said by one of the people in the groups
>>>
>>>
>>> On Sat, Dec 20, 2008 at 9:15 PM, lakesh <lak...@gm...>wrote:
>>>
>>>> Hi Abhishek,
>>>>
>>>> I was tuning the parameters of the Gabor filters and I think I got some
>>>> improvements. I changed the window size and the threshold and some other
>>>> parameters. There is slight improvement; however we can tune the parameters
>>>> to any thing we want that is we can overfit it to a specific image. Also
>>>> other thing is that we don't need to get the high energy points to the
>>>> specific locations like  eyes,nose mouth etc. I got some papers where they
>>>> have used adaboost for feature selection and the features are located at
>>>> random locations like us. Also in most of the papers they have taken
>>>> frequency as sqrt(2). The ebgm paper has also taken the same frequency. Also
>>>> I think while comparing the responses of the images to get the feature point
>>>> we should use directly the magnitude. I mean when we shift through the image
>>>> using the window of size WxW to compare the results, we should use the
>>>> magnitude of the response for the comparison and not directly the complex
>>>> numbers. I tried to compare the complex number and it considers only the
>>>> real part while doing the comparison. So I think it is not the correct way
>>>> to compare. Though in Kepenekci  it seems like they have directly compared
>>>> the complex numbers, I think we should use the magnitude values directly.
>>>>
>>>> Lets sit and discuss the parameter selection when you finish the C++
>>>> implementation.
>>>> Currently I am laying my hands with everything I can  find and checking
>>>> the results.
>>>>
>>>>
>>>>
>>>> On Sat, Dec 20, 2008 at 8:46 PM, Abhishek Dutta <
>>>> the...@gm...> wrote:
>>>>
>>>>> Hi lakesh,
>>>>> I decided to use "vigra<http://kogs-www.informatik.uni-hamburg.de/%7Ekoethe/vigra/>"
>>>>> library instead of GSL. GSL was not sufficient and did not fulfill all our
>>>>> requirements.
>>>>>
>>>>> "vigra" allows to generate gabor filter family by just supplying the
>>>>> no. of orientations, scale and center frequency. According to the "vigra"
>>>>> documentation, center frequency should not exceed 0.375. However, I was
>>>>> using sqrt(2) = 1.414 as frequency in matlab implementation. Moreover, it
>>>>> selects the best gaussian function (the sigma that we needed to supply)
>>>>> based on a mathematical formula (that I didn't understand). The output (at
>>>>> image size 128x128) looks good. But this does not assure better final
>>>>> results. I will update you with final results after I complete the code to
>>>>> compute feature vectors.
>>>>>
>>>>> bye
>>>>>
>>>>> --
>>>>> Abhishek
>>>>> http://adutta.np.googlepages.com
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Have a nice day
>>>>
>>>
>>>
>>>
>>> --
>>> Have a nice day
>>>
>>
>>
>>
>> --
>> Have a nice day
>>
>>
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>>
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>
>
> --
> Anjan Nepal
>
> GPO Box 11458
> Registered Linux User #395963
>
>


-- 
Abhishek
http://adutta.np.googlepages.com