This functionality of the graphs of Excel allows "to model" sets of experimental points: From the experimental points (1 column of abcisses X and one or more columns of ordinates Y): Trace a graph "scatter plot" (Select columns and then  launch the graphic wizard )

Right-click on one of the points of the scatter plot and then launch "Add a trendline" ("Ajouter une courbe de tendance").

Choose the type of model, On the tab "options", activate if required: - "Display the equation on the graph" - and "Display the coefficients of determination". These parameters may then be modified while clicking with the right button on the trendline.