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

In summary, the conversation is discussing how to obtain the equation of a plotted curve without using a trend line. The individual has already used the log-Pearson Type III Distribution to fit the red points and does not need to use any additional trend lines in Excel. They suggest using a method in Excel involving entering parameters, calculating residuals, and using the solver to minimize the sum of squares.
  • #1
median27
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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.
 

Attachments

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    log P.png
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  • #2
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.
 

1. How do I find the equation of a plotted curve in Excel?

To find the equation of a plotted curve in Excel, you will need to use the "Trendline" feature. Right-click on your plotted data points and select "Add Trendline." From there, you can choose the type of equation you want to use (such as linear or exponential) and Excel will automatically calculate the equation for you.

2. Can I manually enter an equation for my plotted curve in Excel?

Yes, you can manually enter an equation for your plotted curve in Excel by using the "Insert Function" feature. Type in the name of the equation you want to use (such as "LINEST" for linear regression) and follow the prompts to enter your data and calculate the equation.

3. How accurate is the equation calculated by Excel for a plotted curve?

The accuracy of the equation calculated by Excel for a plotted curve depends on the quality and quantity of your data points. Generally, the more data points you have, the more accurate the equation will be. It's always a good idea to check the equation against your plotted data to ensure it is a good fit.

4. Can I edit the equation of a plotted curve in Excel?

Yes, you can edit the equation of a plotted curve in Excel by right-clicking on the trendline and selecting "Format Trendline." From there, you can adjust the equation's parameters, such as the intercept or slope, to better fit your data.

5. What should I do if the equation of my plotted curve in Excel is not accurate?

If the equation of your plotted curve in Excel is not accurate, you may need to adjust the type of equation you are using or consider using a different equation altogether. You can also try adding more data points or adjusting the data range to see if that improves the accuracy of the equation.

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