Plotting the frequency response of a filter in "real" Hz

[Guilherme Ritter]

Hi everyone.

I've just started in filter design at college and I'm learning to use Octave for it. I want to see the frequency response of filters I design. I've managed to find code on the internet, but the output's x axis is in radian frequency. I'd like it to show "actual" Hz. For example, if the cutoff frequency is 5,5 kHz, I'd like for it to be represented in the plot's x axis at 5500 or 5,5.

I've searched a lot but couldn't find anything, only some solutions that work in MatLab but not in Octave. At college, I'm using Octave 4.0.0, packages control 3.0.0 and signal 1.3.2, Windows 7 Enterprise x64. At home, all the versions are up to date, Xubuntu 14.04 x64.

I've found the code here:

https://ccrma.stanford.edu/~jos/fp/Example_LPF_Frequency_Response.html

Can I use Octave's functions to get that plot the way I want it?

Thanks in advance.