Background: I am working with pump curves in a hydraulic model. The model is written on excel. In the model pump curves are defined using tested flows vs. dynamic head (ft). The problem I am having is an iterative solution to fit an equation to the data points. Once the first equation is fit to the data points I skew them slightly to induce the R^2 value to 1. Each time I move a data point the best fit equation changes respectively with the order of the equation. The higher the order, the more accurate, hence the more the equation changes each time a data point is moved. All in all I need to find how excel models the best fit line and comes up with the equation they use so I can experiment with a macro to do the iterative process. Can anyone help?