Petrology class project in R and Excel

My 2 unit self-study assignment this semester was to create a project for the G310/510 class that would take one full class week (4 hours total) for the students to complete. My G510 grade for the project depended on my ability to grade the finished assignments. I report that my project was a success, and I am publishing it here.

R: Spider diagrams

Creating a spider diagram in R is not a trivial task. A spider diagram is a multi-line chart, or geology’s version of a parallel axes plot. Spider diagrams are used to see if the lava is depleted or enriched in REE (rare earth elements) compared to some normative rock (chondrite meteorite; depleted mid-ocean ridge basalt, or NMORB; primitive mantle; etc.). The x-values are the elements of interest, and the y-values are plotted on a logarithmic scale. The normalizing values therefore plot as a horizontal line at 1.