This page performs a discrete fast Fourier transform on real data and
plots
both the input waveform and the 'power' output. Since the algorithm is
based on a fast Fourier transform (FFT), the number of input points is
limited to a power of two. Points beyond a power of two are discarded;
for example, if 100 points are input, only 64 (2^6) points are used.
The output includes a listing of the input as a
check, and the sine and cosine components for the transform. The
'power' is calculated as the square root of the sum of the squares of
the sine and cosine
component; these are the values plotted on the second graph. Since the
listings are delimited with tab characters, they can readily be
exported into a spreadsheet.
Graphing uses the Canvas tag, which may not be available in some older
browsers. The algorithm is in Javascript and can be viewed within the
source of the page.
Jeffrey Clymer -- July 4, 2011. Revision 2, July 6, 2011 -- Email
-- Homepage