GPJ - Grapher Project File is a file extension in which you can download free of charge just by going online. Grapher is a program that you must have in order to benefit form this program in any type of way. It is mainly used for generating both 3D and 2D graphs. With this extension, you can do a lot more, and are also given a lot more options.
This extension allows users to be able to store the source data and the visual graph that are used to make the graph look generated. If you do not have the extension, you may only be able to store the visual graph and not the entire source data.
You can also use this extension to generate visuals that have to do with technical publications and even presentations. When you are finished creating what you want with this extension, you can then use your graphs for many different things. The file alone can be used to save bar graphs, line graphs, and even scatter graphs. You can use this for box whisker graphs, and many others that are more advanced. This extension definitely comes in handy when you need it the most.