Hi, i'm not a mathematician at all so I'm sorry for not using correct jargon. I need to create functions that give a specified output. I'm able to draw the graphs that should correspond with the output values of the function, however I haven't got a clue how to get the corresponding function... The functions I need to create produce a single value from a single parameter. The parameter specifies a date or a number of days from a starting point. A very good example: I need a function that gives the percentage of extra protein need during a workout program. This graph (http://www.vspop.org/images/graph09.jpg) shows a nice example of a graph that i can produce. What is tells is that during the first days of the workout program, the percentage should gradually be increased. After a certain maximum value, the percentage should gradually drop to zero again... Is there a way to get a function from a graph? Or is there special software available which takes this reversed approach? Thank you all.