MHB How to workout the exponential curve using x and y values and without excel

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To find an exponential curve equation using only x and y values, it's important to note that the provided y-values are nearly constant, which suggests they may not fit an exponential model well. The presence of an outlier in the data could significantly distort any curve fitting attempts. While there are methods to calculate exponential equations without Excel, they may require extensive manual calculations. The overall fit for both exponential and linear models is poor, with an r² value around 0.5, indicating unreliable results. Consulting with an instructor for guidance on the data's suitability for exponential modeling is advisable.
masterims
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Hi All,

I have searched for hours but cannot figure this out. I need to find the equation for an exponential curve but I only have the x and y values. Is there a way to do this without using excel?

I tried to follow this on YouTube: https://www.youtube.com/watch?v=ta4MZS7w2VA but the equation I got for the data below was different to what excel produces.

x......y
78.46......99.572
90.12......99.56
107.61......99.545
101.78......99.531
119.27......99.514
101.78......99.5
113.44......99.484
107.61......9.469

Thank you,
Imran
 
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masterims said:
Hi All,

I have searched for hours but cannot figure this out. I need to find the equation for an exponential curve but I only have the x and y values. Is there a way to do this without using excel?

I tried to follow this on YouTube: https://www.youtube.com/watch?v=ta4MZS7w2VA but the equation I got for the data below was different to what excel produces.

x......y
78.46......99.572
90.12......99.56
107.61......99.545
101.78......99.531
119.27......99.514
101.78......99.5
113.44......99.484
107.61......9.469

Thank you,
Imran

Hi masterims! Welcome to MHB! :)

Yes, there are other ways than to use Excel.
Actually, you can use Excel in other ways to find an exponential equation.

But before we go there, let's start with your data points.
From visual inspection, I can see that your x-data is distributed with a reasonable range.
However, your y-data is nearly constant (with 1 exception).
So it doesn't seem to match an exponential curve at all.

Moreover, you have a far outlier in your last data point.
Whatever you do, this will have a disastrous effect on any exponential curve match.
 
masterims said:
Hi All,

I have searched for hours but cannot figure this out. I need to find the equation for an exponential curve but I only have the x and y values. Is there a way to do this without using excel?

I tried to follow this on YouTube: https://www.youtube.com/watch?v=ta4MZS7w2VA but the equation I got for the data below was different to what excel produces.

x......y
78.46......99.572
90.12......99.56
107.61......99.545
101.78......99.531
119.27......99.514
101.78......99.5
113.44......99.484
107.61......9.469

Thank you,
Imran
I'm going to assume that the y value for the x = 107.61 data point is a typo (y = 99.459?), not an outlier. However the exponential fit and the linear fit to the data are both horrible: I get r^2 = 0.5 (or so) for both fits. So it doesn't matter what method you use...I can't think of a way to do it without Excel, unless you wish to do some time consuming calculator work. But seeing as you are going to get lousy results, I'd say talk to your instructor first.

-Dan
 

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