Signal is install but it doesn't work

[Matthieu MORISSE]

Dear Octave support, 

I have GNU Octave, version 4.0.3 on my MacBook Pro with macOS Sierra 10.12.3. 

In the contexte of my work, I need to create filter, that's why I installed the package control 3.0.0 and signal 1.3.2. Of course, I loaded before launch my program. 

However, I have this message : 

>> Sensor

warning: the 'dfilt' function belongs to the signal package from Octave Forge but has not yet been implemented.

Please read <http://www.octave.org/missing.html> to learn how you can

contribute missing functionality.

warning: called from __unimplemented__ at line 524 column 5

Sensor at line 9 column 4

error: 'dfilt' undefined near line 9 column 6

error: called from

 Sensor at line 9 column 4

>> pkg list

Package Name  | Version | Installation directory

--------------+---------+-----------------------

    control *|   3.0.0 | /Users/Shiva/octave/control-3.0.0

            io *|   2.4.5 | /Users/Shiva/octave/io-2.4.5

     signal *|   1.3.2 | /Users/Shiva/octave/signal-1.3.2

What I have to do to resolve this problem and use dfilt function ? 

Thank you for your help

Best Regards, 

Matthieu MORISSE