Fwd: Want to know how to inluce octave fft lib in my Qt program

[Prasanth N P]

On Tue, Oct 22, 2013 at 4:33 PM, c. <address@hidden> wrote:

On 22 Oct 2013, at 12:17, Prasanth N P <address@hidden> wrote:

> Ok it work fine, but actually I just want the absolute value of those result.
>
>
>
>   octave_value_list output = feval ("fft", input, 1);
>
>   octave_value_list final_output = feval ("abs", output, 1);
>
>   ColumnVector output_vector = final_output(0).column_vector_value ();
> Is this the right method?

yes, if you want to do it through the Octave interpreter that is the correct approach,
otherwise you cajust do:

  ColumnVector output_vector = output(0).complex_column_vector_value ().abs ();

> How can I study these octave datatypes? Is any tutorial avialable for this octave c++ API?

there are some basic examples in the manual

  http://www.gnu.org/software/octave/doc/interpreter/Oct_002dFiles.html#Oct_002dFiles
  http://www.gnu.org/software/octave/doc/interpreter/Standalone-Programs.html#Standalone-Programs

and this presentation:

  http://wiki.octave.org/wiki/images/b/b0/Slides_octconf_gdf_jgh.pdf

but, as Octave is Free software and teherfore you are granted the freedom to study the sources,
the best option is to look at the code directly:

  http://hg.savannah.gnu.org/hgweb/octave/file/5b0036d89d4a

or through Doxygen

  http://octave.sourceforge.net/doxygen/html/index.html
  http://octave.sourceforge.net/doxygen/html/d3/de3/classComplexColumnVector.html


HTH,
c.

Hi,

The result set is completely different from that produced by octave prompt. Is this is the mistake of incorrect data extraction?

In octave prompt, my program is

load 'buffer'

setenv ("GNUTERM", "x11")

l=1024;

v=fft(buffer,l);

V = abs(v);

save output V;

will produce output

 29836655360

 7194618843.804271

 31222458039.80829

 6504667191.029741

 32288941967.04408

 9843961135.068363

 30983143293.79837

 7611290380.697447

 4861098750.903645

 3324109517.901031

 7207271566.692511

 3908976136.391438

 6415257024.785824

 etc.....

and the same input in c++,

  FILE *fp;

  fp = fopen("buffer","r");

  if (fp == NULL)

  return 0;

  

  for (ucI=0; ucI< 1024; ucI++)

    fscanf(fp, "%d\n", input_vector.fortran_vec () + ucI);

  fclose(fp);

  

  

  

  octave_value_list input;

  input(0) = input_vector;

  octave_value_list output = feval ("fft", input, 1);  

  octave_value_list final_output = feval ("abs", output, 1);

    

   

  ColumnVector output_vector = final_output(0).column_vector_value ();

  for (ucI=0; ucI< 1024; ucI++)

printf("%d\n",output_vector.fortran_vec () [ucI]);

will produce

-228115712

-2036061617

-41838449

2021575525

559518313

-452798453

994969983

610738633

2046297242

-430100987

-2078919967

567105869

617583034

288730045

etc...

What to do?