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Topic: How to fit a sine wave to under-sampled data
Replies: 3   Last Post: Jan 7, 2013 9:38 PM

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Greg Heath

Posts: 6,167
Registered: 12/7/04
Re: How to fit a sine wave to under-sampled data
Posted: Dec 27, 2012 7:56 PM
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"Scott Rauscher" wrote in message <kbg0a3$afm$1@newscl01ah.mathworks.com>...
> I've poured through the forums several times and have almost found a good solution.
> I want to fit a sine wave to some under-sampled constant-frequency/phase/amplitude data. I have hundreds of data files so I need to automate it. I have used SineFit in the file exchange, and it works well most of the time, but has a tendency not to converge. I have also tried sinfapm, but the phase it gives never lines up.
> What I'm trying to do is best illustrated in this picture (red is the data, blue is the sine wave I want to find): http://s2.postimage.org/98qvgbnu1/matcode.jpg
> Does anyone have suggestions on where to start for a full-proof way of doing this?

Not enough info.

Do you get a dominant frequency with the dft ? If so, you can estimate A and B
from the linear problem

xi = A*cos(w*ti) + B*sin(w*ti); % w and ti known

Hope this helps.


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