One area where Excel is different from a graphing calculator is in producing the graph of a function that has been defined by a formula. This is a range of cells of numeric independent values. Alternatively you can calculate the slope using the LINEST function.
That adds r squared to the graph just below the equation as in the snapshot below.
We can add an equation to a graph in excel by using the excel equation of a line. Select the Label drop-down and select Use Equation. We are all set to calculate the SLOPE of this data. Using the SLOPE function.