-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hello World ! I have a question about FastFourierTransformer. I'm unable to retrieve fundamental frequency of the fft. Mathematically, it could be 2π / samble size, but this formula doesn't seems working. I apply FFT to a 1Hz sinus, sampled at 20Hz during 1 minute. So sample size is 1.200, zero-padded to 2.048 (upper 2-pow), and fundamental could be 3mHz (2π / 2.048). Theorical FFT of this sinus must be 2 peaks, at f = -1Hz and f = 1Hz. But obtained FFT presents 2 peaks, at n ~ 100 and n ~ 1950, so f = (100-1024) × 3mHz ~ -5,66Hz and f = (1950-1024) × 3mHz ~ 5,66Hz. Seems the mathematical theory doesn't apply here… Stranger, FFT on 0.1Hz sinus presents 2 peaks at n ~ 10 and n ~ 2030, leading to f ~ ±6,22Hz… A signal at a lower frequency leads to an FFT at a higher spectrum… So, am I wrong somewhere ? And how I can calculate the fundamental frequency from FastFourierTransformer.transform(double[]) ? Thanks in advance - -- Aeris -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iQEcBAEBAgAGBQJOGacsAAoJEK8zQvxDY4P9bG8H/37IQNk3JSfJuC0rANI/u+z4 mj77jgtLnGEnG0ys5oNFu3KcGgguipUB7hpgHTvbN45owJjqqmSBC87O8XxAZQ+M x+7wsW0kkvcgTncN5nLdd0Uukjrhfuf1q5yN82MWNQqs7LI5+Rzzs1eU1tmGU8hW Tjj5ExAIb0wWUQoelRPMiFXQTAXtVyr69mDRlD9qPtlir9zDYQEhgF51OuyU1TaO 8yD3CThekQ8agk0jqlgMhX4Wgw9lSG3X0bMi8POYCLdC583SaUFmxZg+XqSwc8K1 dVypVHtzRDfHIKwVHOW0BzsI7V11qPMejdJx3Lhd0kDabftpoP2DIKbpc7IXOa0= =ge5K -----END PGP SIGNATURE----- --------------------------------------------------------------------- To unsubscribe, e-mail: user-unsubscribe@commons.apache.org For additional commands, e-mail: user-help@commons.apache.org