Can anybody tell me how I make a FFT-Transformation in Excel?
I have never used an AddIn before and so I don't know how to
do ist.

Hi. Not sure what version you have.
Prior to Excel 2007, you first select Tools | AddIns, and select Data
Analysis.
Then, go back and select Tools | Data Analysis. The Fourier Program is
about half way down the list.

If you are getting an error, just note that the program does not work with
blank data. Excel does not make the assumption that blank cells have a
value of zero. You have to put a value in each of the 128 cells.

If you are having a problem transforming the output into Sin/Cos Trig
functions, note that there are different definitions of a fft. In Excel,
note that the first output is the "Sum" of your data. Excel's equation is
useful in Signal Processing, but not Data Analysis. An easy fix is to just
divide the output by the size of your data. =IMDIV(B1,128)

To find any dominate frequencies, a common technique is to take the Abs
value of each complex number.
=IMABS(B1)

Plot these values using x-y scatter chart.
Those frequencies that contribute the most will have a larger Abs value or
"Peak".

--
HTH :)
Dana DeLouis
Windows XP & Excel 2007


"maqqusz" wrote in message
...
Hi,

Can anybody tell me how I make a FFT-Transformation in Excel?
I have never used an AddIn before and so I don't know how to
do ist. My Values [2] I want to transform are yearly Temperatures
from 1980 to 2006, so the Imaginary-value may be zeros.

How do I do such a Transformation. There are 127 Values
so if I add one unknown more it should be possible.

[1] http://home.arcor.de/maqqusz/wetterr...temperatur.png
[2] http://home.arcor.de/maqqusz/wetterr...Temperatur.xls
[3] http://home.arcor.de/maqqusz/wetterr...Temperatur.txt

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