Install gri-html-doc by entering the following commands in the terminal:
sudo apt update sudo apt install gri-html-doc
Description:
HTML manual for gri, a language for scientific graphics
Gri is a command-driven application for making x-y graphs, contour-graphs, and image graphs. . This is the Gri manual in HTML format and can be accessed directly via file:/usr/share/doc/gri/html/index.html or http://localhost/doc/gri/html/ or via doc-central, dwww or dhelp interfaces (if you have the doc-base package installed). Note that the manual in info format (without graphics) is included in the gri package itself. This manual is available on the web via: http://gri.sourceforge.net/gridoc/html/
Homepage: http://gri.sourceforge.net/
Version: 2.12.26-1build1
Section: universe/doc