Nyquist frequency signal, whereas "Nyquist frequency" is a property of a discrete-time system. When the function domain is time, sample rates are usually expressed in samples per second, and the unit of Nyquist frequency is cycles per second (hertz). When the function domain is distance, as in an image sampling system, the sample rate might be dots per inch and the corresponding Nyquist frequency would be in cycles/inch. Referring again to Figure 1, undersampling of the sinusoid at 0.6 f is what allows there to be a lower-frequency "alias", which is a different function that produces the same set of samples. That
Oh Dear! What Can the Matter Be? basin it was the same water the next washed her face in – and nobody knew they were there. </poem> "Seven Old Ladies" was not the first parody, however. Long before that parody, the song had been parodied for political purposes. One such parody can be found in the "Wisconsin State Journal" of 1 March 1864. It was written to exhort parents, who during the U.S. Civil War had not taken much interest in public schooling in Madison, to visit the schools of their children. Its lyrics were: <poem> Oh, dear, what can the matter be? Oh, dear, what can