You might need to clarify your question. For trend analysis, you should specify what data you are trying to visualize the trends. Project data can be broken down many ways.
For things like cost trends or burndown/burnup charts, typically I would expect to see plan vs. actuals as a minimum. If someone wants to extrapolate that into the future, they usually either just fit a line to the entire curve, or fit a line to the last few data points and project that into the future.
Commodity curves can mean different things to different people. I work with many technical teams (e.g. hydraulics, control systems, structures, etc.) and each one is called a commodity. We track by-team performance data in addition to the whole project. Commodity curves are also used in financial analysis to track the cost of commodities like raw material costs that could dictate the NPV of your project over time. Normally that's not a PM function in my environment, but with today's market instabilities it could certainly have a large impact on project financial outcomes. Saving Changes...
