Excel - 获取连接三点的曲线方程

Question

I have three points (Year, growth) and I would like to find an equation connecting them in Excel:

Point 1: (2016, 3033%)
Point 2: (2017, 397%)
Point 3: (2023, 20%)

Is there a way to do it on Excel. I tried power 4 quadratic equation using Linest(Range1, Range2^{1,2,3,4}) but I have an area of growth below zero. Not a curve that drops sharply between 2016 and 2017 before stabilizing between 2017 and 2023. Growth cannot be negative on this case. I would like to build equations so that if user change the growth in 2023 for example it will automatically modify the function and so 2018, 2019, 2020, 2021 and 2023 can be found. Anybody knows how to do on Excel please? Thank you

Answer 1

You probably need to fit your table to an exponential function that has a negative coefficient for the variable of the exponent, ie y = A exp(-bx)

You can use the LINEST() function in excel to do that if you linearize the equation: lny = lnA + bx

A scatterplot with a linear trendline will also give you the coefficient. Take a look athttps://www.engineerexcel.com/nonlinear-curve-fitting-in-excel/