Fourier Analys

[Ed_Berez]

Hi,
I need more than 4096 values in the input range of the Fourier Analysis.
Please, help.

[Steve Dalton]

Could you provide more details?

Where is the Fourier Analysis being done (workbook, VBA, other) and by what
(3rd party add-in, your own code, other)?

Regards

Steve Dalton


"Ed_Berez" <[email protected]> wrote in message
news:[email protected]...
> Hi,
> I need more than 4096 values in the input range of the Fourier Analysis.
> Please, help.

[Ed_Berez]

Hi, Steve.

I use Fourier Analysis from Data Analysis tool pack (Tools>>Data
Analysis>>Fourier Analysis). The maximum number of values in the input range
is 4096. (The number of input range values must be an even power of 2).

Regards.

"Steve Dalton" wrote:

> Could you provide more details?
>
> Where is the Fourier Analysis being done (workbook, VBA, other) and by what
> (3rd party add-in, your own code, other)?
>
> Regards
>
> Steve Dalton
>
>
> "Ed_Berez" <[email protected]> wrote in message
> news:[email protected]...
> > Hi,
> > I need more than 4096 values in the input range of the Fourier Analysis.
> > Please, help.
>
>
>

[Myrna Larson]

In that case, you can't modify the limitations. YOu would have to write your
own function or use a 3rd party add-in.

On Sun, 13 Feb 2005 12:09:07 -0800, "Ed_Berez"
<[email protected]> wrote:

>Hi, Steve.
>
>I use Fourier Analysis from Data Analysis tool pack (Tools>>Data
>Analysis>>Fourier Analysis). The maximum number of values in the input range
>is 4096. (The number of input range values must be an even power of 2).
>
>Regards.
>
>"Steve Dalton" wrote:
>
>> Could you provide more details?
>>
>> Where is the Fourier Analysis being done (workbook, VBA, other) and by what
>> (3rd party add-in, your own code, other)?
>>
>> Regards
>>
>> Steve Dalton
>>
>>
>> "Ed_Berez" <[email protected]> wrote in message
>> news:[email protected]...
>> > Hi,
>> > I need more than 4096 values in the input range of the Fourier Analysis.
>> > Please, help.
>>
>>
>>

[Ed_Berez]

Could you please advise me any 3rd party add-in to solve my problem?


"Myrna Larson" wrote:

> In that case, you can't modify the limitations. YOu would have to write your
> own function or use a 3rd party add-in.
>
> On Sun, 13 Feb 2005 12:09:07 -0800, "Ed_Berez"
> <[email protected]> wrote:
>
> >Hi, Steve.
> >
> >I use Fourier Analysis from Data Analysis tool pack (Tools>>Data
> >Analysis>>Fourier Analysis). The maximum number of values in the input range
> >is 4096. (The number of input range values must be an even power of 2).
> >
> >Regards.
> >
> >"Steve Dalton" wrote:
> >
> >> Could you provide more details?
> >>
> >> Where is the Fourier Analysis being done (workbook, VBA, other) and by what
> >> (3rd party add-in, your own code, other)?
> >>
> >> Regards
> >>
> >> Steve Dalton
> >>
> >>
> >> "Ed_Berez" <[email protected]> wrote in message
> >> news:[email protected]...
> >> > Hi,
> >> > I need more than 4096 values in the input range of the Fourier Analysis.
> >> > Please, help.
> >>
> >>
> >>
>
>

[Dan Bullard]

I can give you some C Code that you can modify into VBA code and make you're own FFT. I may give this a try myself and when (if?) I get it working I can post it. Here is the FFT, also required is a BitReverse function and another one which calculates the number of samples required which are also enclosed.

void fft_double (
unsigned NumSamples,
double *RealIn,
double *RealOut,
double *ImagOut )


{
unsigned NumBits; /* Number of bits needed to store indices */
unsigned i, j, k, n;
unsigned BlockSize, BlockEnd;
double angle_numerator = 2.0 * PI;
double tr, ti; /* temp real, temp imaginary */
double delta_angle;
double sm2;
double sm1;
double cm2;
double cm1;
double w;
double ar[3], ai[3];
double *RealTmp = new double[NumSamples];
double *ImagTmp = new double[NumSamples];


if ( !IsPowerOfTwo(NumSamples) )
{
fprintf (
stderr,
"Error in fft(): NumSamples=%u is not power of two\n",
NumSamples );

return;
}

//CHECKPOINTER ( RealIn );


NumBits = NumberOfBitsNeeded ( NumSamples );

/*
** Do simultaneous data copy and bit-reversal ordering into outputs...
*/

for ( i=0; i < NumSamples; i++ )
{
j = ReverseBits ( i, NumBits );
RealTmp[j] = RealIn[i];
ImagTmp[j] = 0.0;
}

/*
** Do the FFT itself...
*/

BlockEnd = 1;

for ( BlockSize = 2; BlockSize <= NumSamples; BlockSize <<= 1 )
{
delta_angle = angle_numerator / (double)BlockSize;
sm2 = sin ( -2 * delta_angle );
sm1 = sin ( -delta_angle );
cm2 = cos ( -2 * delta_angle );
cm1 = cos ( -delta_angle );
w = 2 * cm1;

for ( i=0; i < NumSamples; i += BlockSize )
{
ar[2] = cm2;
ar[1] = cm1;

ai[2] = sm2;
ai[1] = sm1;

for ( j=i, n=0; n < BlockEnd; j++, n++ )
{
ar[0] = w*ar[1] - ar[2]; ar[2] = ar[1]; ar[1] = ar[0];
ai[0] = w*ai[1] - ai[2]; ai[2] = ai[1]; ai[1] = ai[0];

k = j + BlockEnd;
tr = ar[0]*RealTmp[k] - ai[0]*ImagTmp[k];
ti = ar[0]*ImagTmp[k] + ai[0]*RealTmp[k];

RealTmp[k] = RealTmp[j] - tr;
ImagTmp[k] = ImagTmp[j] - ti;

RealTmp[j] += tr;
ImagTmp[j] += ti;
}
}

BlockEnd = BlockSize;
}

// added to remove requirement to pass full size real and image arrays to FFT
// and to rescale to the right value

double denom = (double)(NumSamples)/2.0;
for(i=0; i<j; i++)
{
RealOut[i] = RealTmp[i]/denom;
ImagOut[i] = ImagTmp[i]/denom;
}

RealOut[NumSamples/2] = RealTmp[NumSamples/2]/(denom*2);
ImagOut[NumSamples/2] = ImagTmp[NumSamples/2]/(denom*2);


delete RealTmp;
delete ImagTmp;
}


unsigned ReverseBits ( unsigned index, unsigned NumBits )
{
unsigned i, rev;

for ( i=rev=0; i < NumBits; i++ )
{
rev = (rev << 1) | (index & 1);
index >>= 1;
}

return rev;
}


unsigned NumberOfBitsNeeded ( unsigned PowerOfTwo )
{
unsigned i;

if ( PowerOfTwo < 2 )
{
fprintf (
stderr,
">>> Error in fftmisc.c: argument %d to NumberOfBitsNeeded is too small.\n",
PowerOfTwo );

return(1);
}

for ( i=0; ; i++ )
{
if ( PowerOfTwo & (1 << i) )
return i;
}
}

[6StringJazzer]

Dan Bullard, it is very unlikely that he is still looking for the solution nine years later. In addition, the OP was cross-posted without a link. As for your post, please take the time to review our rules. There aren't many, and they are all important.

Your post does not comply with Rule 3 of our Forum RULES. Use code tags around code.

Posting code between [CODE]Please [url=https://www.excelforum.com/login.php]Login or Register [/url] to view this content.[/CODE] tags makes your code much easier to read and copy for testing, it also maintains VBA formatting.

Highlight your code and click the # icon at the top of your post window. More information about these and other tags can be found here



Given the multitude of transgressions here I'm closing this zombie thread.