freqz issue

[Laurent HAAS - F6FVY]

Hi

I'm trying to experience basic signal processing with Octave, while the 
original article has been written for Matlab

http://aaronscher.com/wireless_com_SDR/RTL_SDR_AM_spectrum_demod.html

I'm actually facing this issue :

In the "Plot the spectrum" section,

freqz(y(1:5000),1,[-4E6:.01E6:4E6],2.5E6);

keeps the spectrum totally blank, and returns this error :

>> freqz(y(1:5000),1,[-4E6:.01E6:4E6],2.5E6);
error: __plt2vv__: vector lengths must match
error: called from
    __plt__>__plt2vv__ at line 482 column 5
    __plt__>__plt2__ at line 242 column 14
    __plt__ at line 107 column 18
    plot at line 223 column 10
    freqz_plot at line 55 column 3
    freqz at line 194 column 5
>>

I'm running Octave 5.1.0 under Win7-32 bit

What am I missing ?

Thanks and regards

--

I never lose. I either win or learn - Nelson Mandela