I was looking for a more efficient way of finding the magnitude and phase of a signal at a certain frequency without performing an FFT because it produces more information than I need and I came across this comment on the Matlab message board:
http://www.mathworks.com/matlabcentral/newsreader/view_original/250421.
If I am sampling at 1500Hz and my signal is 100 points and I am looking for the phase and magnitude at 15Hz, would this be suitable method for obtaining the information I need? Also, why does the OP suggest windowing the signal as well?
You might want to check the Goertzel algorithm: http://en.wikipedia.org/wiki/Goertzel_algorithm It is actually part of the matlab signal processing toolbox.