Is it possible to generate a trendline equation without drawing a graph?
I have a column that is missing about 30 data points, I'd like to fill the blanks based on a trendline of the existing data
Excel's functions "FOR3ECAST" or "TREND" (using array-formulae) will get you what you want assuming the trend is linear.
By futzing with the data, you may be able to get a polynomial curve fitting .
This taken from Excel Help:
Calculates, or predicts, a future value by using existing values. The predicted value is a y-value for a given x-value. The known values are existing x-values and y-values, and the new value is predicted by using linear regression. You can use this function to predict future sales, inventory requirements, or consumer trends.
*Returns values along a linear trend. Fits a straight line (using the method of least squares) to the arrays known_y's and known_x's. Returns the y-values along that line for the array of new_x's that you specify.*