On 17/09/2009, at 3:39 AM, delic wrote:


I wrote a script that I anticipating seeing a spike at  10Hz with the
function 10* sin(2*pi*10*t).
I can't figure out why my plots do not show spikes at the frequencies I
expect. Am I doing something wrong or is my expectations wrong?

(a) Is this a homework question?

(b) Have you figured it out yet?

(c) Hint: You have spikes at +/- 40 in a range from -50 to 50. You *want* spikes at 10 and 90 Hz. Could it be that you haven't set your frequency vector ``f''
quite right? :-)

        cheers,

                Rolf Turner

P. S. You won't get spikes bang on at 10 and 90 Hz. because these are *not* Fourier frequencies when n = 256. If you want spikes in your periodogram at bang on 10 and 90 Hz use a value of n that is divisible by 10, e.g. n=500. Why would you want a power of 2 anyhow? (Well, the fft goes faster when n
is a power of 2, but who cares?)

                R. T.

######################################################################
Attention:\ This e-mail message is privileged and confid...{{dropped:9}}

______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

Reply via email to