How to get the equation of the plotted curve in Excel?

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To obtain the equation of a plotted curve without using a trend line, one effective method involves fitting the data using the log-Pearson Type III Distribution. Instead of relying on Excel's built-in trend line features, users can manually input the parameters of the desired distribution into specific cells. By calculating the residuals, which represent the differences between the fitted equation and the actual data points, and then squaring these residuals, users can sum them to find the total error. Excel's Solver can then be utilized to minimize this sum of squares by adjusting the parameters, leading to an optimal fit for the curve. This approach allows for a more tailored fitting process that aligns with specific distribution models.
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How can I get the equation of the plotted curve (see attachment) without using the trend line?
I've already fitted the random red points using the log-Pearson Type III Distribution (and the result is the blue curve) so I don't need to fit them anymore using any trend lines available in excel. Anyone? Thanks.
 

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Something I do in Excel is to put the parameters of whatever you are trying to fit into some cells. Then, calculate the residuals (the difference <your equation>-<the data>) into some more cells, where <your equation> is calculated from the parameters you entered. Square the residuals into some more cells. Sum them. Now apply Excel's solver to the parameters and the sum of the squares, trying to minimize the sum.
 

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