Problems in octave 5.1.0 in the function plot

[arkkimede]

Hi!

Few days ago I found the instruction for the installation of Octave 5.1.0 on ubuntu 18.04.

This link report the instructions that I'v used: https://www.math.univ-paris13.fr/~cuvelier/Octave/Ubuntu_18-04LTS.html#x37-75000.9.1

Now I'm octave running on my linux box Ubuntu 18.04.

But I have a problem.

Considering this minimal code:

%--------start

#!/usr/bin/octave -qf

D2R = pi/180.;

ang_d=0:1:360;
ang_r=ang_d*D2R;

h=figure;

plot(ang_d, sin(ang_r));

refresh;

waitfor(h)

%--------stop

If I plot the sine function the line is interrupted.

The same if I use the octave GUI how reported in this screenshot:

https://imagizer.imageshack.com/img921/6600/oCseaa.png

Please could you help me?

PS: I used octave 5.1.0 in Windows and this issu does not present

PS2 I tried also changing graphics_toolkit without results