Forum Discussion
How to create a custom trendline?
Ian_Heath so the basic answer is that you can't input your own 'base' equation for excel to use for the trend line. That said a number of the options do give you the option to set the intercept which can help or change particular characteristics like power of the polynomial. If you have a completely different form then I would set it up as an equation that uses the parameters set in fixed cells and then add another column to calculate the R^2 value for each point and then the sum so you can use the solver (Data -> what-if analysis -> Goal Seek...) to find at least 1 parameter based on minimizing that R^2.
mtarler As you suggested, I could just plot the trendline manually, however, I would still need to calculate the coefficients of the formula to minimise R-squared. Maybe I could use LINEST or something similar to do this.
Ian_Heath so the basic answer is that you can't input your own 'base' equation for excel to use for the trend line. That said a number of the options do give you the option to set the intercept which can help or change particular characteristics like power of the polynomial. If you have a completely different form then I would set it up as an equation that uses the parameters set in fixed cells and then add another column to calculate the R^2 value for each point and then the sum so you can use the solver (Data -> what-if analysis -> Goal Seek...) to find at least 1 parameter based on minimizing that R^2.