`freqspace`

Frequency grid for frequency responses, normalized so that 1 is the Nyquist frequency.

Category: Language Fundamentals > Matrices and Arrays

Syntax

f = freqspace(n)

Frequencies for an n-point response, from 0 up to just below 1.

f = freqspace(n, 'whole')

Covers the whole circle, 0 up to just below 2.

[f1, f2] = freqspace(n)

Frequency vectors for a 2-D response, each from about -1 to 1.

Description

In one dimension the spacing is 2/n, starting at 0, so freqspace(4) gives 0 0.5 1 and freqspace(5) gives 0 0.4 0.8. Multiply by pi to get radians per sample, or by half the sampling rate to get hertz.

The 2-D form returns the spacing used to evaluate filters and windows on a grid; feed f1 and f2 to meshgrid to cover the plane.

Input arguments

n: Number of frequency points (a scalar), or [m n] for a 2-D grid.
'whole': Return the full circle instead of the half up to Nyquist.

Output arguments

f: Row vector of frequencies in units of pi radians per sample.
f1, f2: For the 2-D form, vectors along each frequency axis.

Example

freqspace(4)
freqspace(4, 'whole')
[f1, f2] = freqspace(3);
f1

Output

ans = 1×3

         0    0.5000    1.0000
ans = 1×4

         0    0.5000    1.0000    1.5000
f1 = 1×3

   -0.6667         0    0.6667

freqspace