At the FindGraph library there are more than 200 built-in famous 2-D curves from the areas of elementary mathematics, transcendental functions, probability and statistics, optimization, and graphics.
You can investigate these curves and vary the number of parameters to discover the best model that describe your data.
Click the button or select menu item <Analysis><Famous Function> to create new function. This will cause the Formula dialog box show, where you can modify properties of graph (function, range of parameters, color, width and so on).
You can draw families of lines with a given step of parameter.