$ sudo apt-get update
$ sudo apt-get install octave-lhapdf 

octave-lhapdf is installed in your system.

Make ensure the octave-lhapdf package were installed using the commands given below,

$ sudo dpkg-query -l | grep octave-lhapdf *

You will get with octave-lhapdf package name, version, architecture and description in a table

octave-lhapdf package basic information: