Forum Discussion
How to create a custom trendline?
When none of the trendline options (exponential, linear, logarithm, polynomial, power) fit well, can a different formula be used? If not, can the same be achieved by plotting a custom formula with coefficients adjusted to minimise R-squared?
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.
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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.
