Click See inside to modify the data points, then click the flag to start generating the line. The number of coefficients is the size of the polynomial. ( [1]+[2]x+[3]x^2+[4]x^3... and so on.) If the curve is flat, enter 1. If it's linear, enter 2. If it's exponential, 3. If it's strangely shaped, higher numbers will give you more detail. It takes a minute to find the line, but eventually it will find the solution. If it doesn't find a good enough solution, press R to reset the graph.