I am using OriginPro 8.1 evaluation version in window XP operating system. I would like use the FFT for rainfall analysis. I would like to use FFT to know any periodicity in rainfall. please help me, how to use FFT and how to enter data set. For eg. I would like to know the cyclic shifting of maximum rainfall between July and August during 30 years period for a complete period of 120 years data set.
In 8.1 try the following: 1> with a new workbook/sheet active, use single ascii import to import the file: \samples\signal processing\average sunspot.dat 2> select the 2nd col and make a line plot - this is year-by-year sunspot data 3> select the menu Analysis->Signal Processing->FFT and set what outputs you desire 4> look at amplitude/magnitude for example and you will see a peak at around 0.09 which corresponds to 1/11 so that is the 11-year cycle in sunspots
Under Analysis menu, in Pro, there is also Short-time Frequency analysis tool (STFT) which can do FFT over a sliding window in time.
If you have specific questions, please share your data with us so we could look at it further.
How to use FFT
Posted - 01/26/2010 : 08:47:13 AM
