Forum Discussion

Copper Contributor

Dec 31, 2021

Couldn't calculate exponential trendline intercept value using exponential equation.

With the data below, I am trying to calculate intercept value for exponential trendline with the equation below. But got an error #Num!. Could anyone please help to resolve this. =EXP(INDEX(LINES...

Charting

excel

JoeUser2004

Bronze Contributor

Dec 31, 2021

gayathrimanick wrote: ``Could you please share the complete equation for getting`` the trendline formula.

Adapted from the LINEST function support page, excerpted below.

For LINEST(ln(Y), X), ln(y) = m*x + b, and y = EXP(b) * EXP(m*x), where assuming X is A1:A5 and Y is B1:B5:

for m, array-enter:

=SUMPRODUCT(A1:A5 - AVERAGE(A1:A5), LN(B1:B5) - AVERAGE(LN(B1:B5)))

/ SUMPRODUCT((A1:A5 - AVERAGE(A1:A5))^2)

for b, array-enter (replace "m" with a cell reference):

=AVERAGE(LN(B1:B5)) - m*AVERAGE(A1:A5)

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LINEST function support page excerpt:

gayathrimanick

Copper Contributor

Dec 31, 2021

JoeUser2004 Thanks for the reply. You are right when using datetime for the exponential trendline, the result of the equation tends to EXP(10698.8236831922).

Could you please help? Is there any other way to calculate the intercept value for the exponential trendline? When doing this function EXP(10698.8236831922), I am getting infinity as you said the largest value is about EXP(709.782712893384).

I couldn't draw trendline for the exponential type due to getting infinity for intercept field. Please let me know, is there any other way to calculate intercept value.

Thanks in advance.