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| real part of fft http://forum.alglib.net/viewtopic.php?f=2&t=414 |
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| Author: | sambafr [ Wed Aug 17, 2011 11:05 am ] |
| Post subject: | real part of fft |
Hello, I am new to Alglib, and i am trying to do an fft of the joint positions recieved via Kinect sensor. For each joint i am trying to make 3 FFT of 1 dimension. ( I know it would be better 1 of 3, but i don't see the point for now, so i rather KISS) I was searching for an fft c# library which would simple enough for me to use, Alglib seems very simple Unfortunately, i can not manage to find a simple way to convert the string fft out in an array of only the real part. I know it seems stupid but because of the +/- and i's, i can only find buggy ways. I get to the array of complex numbers in string format, and i then mess everything. Thank you for your help Samba PS: Rather than buying the commercial part, are small donations via paypal possible? |
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| Author: | Sergey.Bochkanov [ Wed Aug 17, 2011 8:12 pm ] |
| Post subject: | Re: real part of fft |
If you want to get real part of the FFT, you should read output_array[i].x - it contains real part. Is it what you need? P.S. As for donations - it is impossible to accept PayPal payments from Russia, unfortunately. If you want, you can e-mail me and tell specific sum you want to donate, and I will send you a link to the special webform used for non-standard payments. (I need to know payments sum and currency beforehand in order to prepare this form) |
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| Author: | sambafr [ Sat Aug 20, 2011 3:26 pm ] |
| Post subject: | Re: real part of fft |
Sergey.Bochkanov wrote: If you want to get real part of the FFT, you should read output_array[i].x - it contains real part. Is it what you need? P.S. As for donations - it is impossible to accept PayPal payments from Russia, unfortunately. If you want, you can e-mail me and tell specific sum you want to donate, and I will send you a link to the special webform used for non-standard payments. (I need to know payments sum and currency beforehand in order to prepare this form) Thank you very much for your answer it was indeed very simple. I took my time because i wanted to be sure that i undestood before answering . If i draw the "power spectrum" of the joint movement via the kinect sensor, therefore i can do: n = total number of recordings ; alglib.fftr1d(timeref, out freqref); Powerspectrum = 2 * Math.Pow((Math.Sqrt(Math.Pow(freqref[i].x, 2) + Math.Pow(freqref[i].y, 2)) / n), 2) Each frequency step = (n / total time) If this is correct, are there any precautions that i should take with n? (should n be a power of 2 for example?) 2:)Concerning donation, it's not much just a way to say thank you, may i pm you for that? 3°) The final objective of my personal project (opensource) is to look for the stability of jointmotion, therefore i would like to use the Lyapunov Exponent to quantify stabilty. I didn' t find any c# library that could help me code that, do you have an advice? EDITT: i saw that alglib can help for nearest neigboor and delay choosing, but i lack the method to go from that to LLE. thanx in advance |
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