f = freqspace(N) returns
the one-dimensional frequency vector f assuming N evenly
spaced points around the unit circle. For N even
or odd, f is (0:2/N:1). For N even, freqspace therefore
returns (N+2)/2 points. For N odd,
it returns (N+1)/2 points.
f = freqspace(N,'whole') returns N evenly
spaced points around the whole unit circle. In this case, f is 0:2/N:2*(N-1)/N.