Hi there.
New to the forum so not sure whether this has been asked before. Sorry if it has.

I have created a graph using six sets of actual sample data. its a simple graph of cost (y) against size (x). As it happens, the larger the item is, the more it costs. (bizarre i know ).
It isnt linear though, and i have used a scatter graph with smoothed lines and the graph is fine.

What i would like to know is this, Is there a way of using the smoothed line i have created to give me costs for other sizes. Ie interpolate between my sample sizes, and give me a cost for any given size?

Or, am i overcomplicating things? Should i be doing it a different way?

hope you can help