Exponential trendline fit in Excel using LINEST - fixing a variable
Exponential trendline fit in Excel using LINEST - fixing a variable
(OP)
I know that you can use the following formulae in Excel to fit a curve using LINEST for the named ranges x and y:
Exponential Trendline
Equation: y = c *e ^(b * x)
c: =EXP(INDEX(LINEST(LN(y),x),1,2))
b: =INDEX(LINEST(LN(y),x),1)
My question is, if I want to fix c=1 can I simply use
b: =INDEX(LINEST(LN(y),x),1) and assume c=1?
Also would it be correct to use
r2: = INDEX(LINEST(LN(y),x),TRUE,TRUE),3)
in this case?
Thanks very much.
Exponential Trendline
Equation: y = c *e ^(b * x)
c: =EXP(INDEX(LINEST(LN(y),x),1,2))
b: =INDEX(LINEST(LN(y),x),1)
My question is, if I want to fix c=1 can I simply use
b: =INDEX(LINEST(LN(y),x),1) and assume c=1?
Also would it be correct to use
r2: = INDEX(LINEST(LN(y),x),TRUE,TRUE),3)
in this case?
Thanks very much.





RE: Exponential trendline fit in Excel using LINEST - fixing a variable
LINEST(known_y's,known_x's,const,stats)
You can force the intercept to be 0 (which is equivalent to c=1) by setting const to FALSE. So your equations should be:
c: =EXP(INDEX(LINEST(LN(y),x, FALSE),1,2))
b: =INDEX(LINEST(LN(y),x, FALSE),1)
This will cause b to be calculated assuming that c = 1.
RE: Exponential trendline fit in Excel using LINEST - fixing a variable
r2: = INDEX(LINEST(LN(y),x),TRUE,TRUE),3)
this is correct in general but you'll want to change it to the following when you for c=1:
r2: = INDEX(LINEST(LN(y),x),false,TRUE),3)
RE: Exponential trendline fit in Excel using LINEST - fixing a variable
RE: Exponential trendline fit in Excel using LINEST - fixing a variable
RE: Exponential trendline fit in Excel using LINEST - fixing a variable
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