Exponential equation extrapolation

Sazzle

New member
Hi. I have some data which yields an exponential relationship between metabolic expenditure and body movements. The curve has an equation "y=26e to the power 0.6x". I would like to learn, please, how to extrapolate x, for when I only know y.
Many thanks in advance.

Dr.Peterson

Elite Member
I think you're saying you want to solve for x, given y. (The equation is already an extrapolation from your data.)

Divide both sides by 26, then take the natural logarithm of both sides. There will be one more easy step after that.

If you need additional help, please let us know where you need help; I can't tell whether you just needed a reminder to use logs, or have forgotten all your algebra!

pka

Elite Member
Hi. I have some data which yields an exponential relationship between metabolic expenditure and body movements. The curve has an equation "y=26e to the power 0.6x". I would like to learn, please, how to extrapolate x, for when I only know y.
If I understand correctly it is $$\displaystyle y=26e^{0.6x}$$. If that is correct then $$\displaystyle x=\frac{\log(y)-\log(26)}{0.6}$$

Sazzle

New member
I think you're saying you want to solve for x, given y. (The equation is already an extrapolation from your data.)

Divide both sides by 26, then take the natural logarithm of both sides. There will be one more easy step after that.

If you need additional help, please let us know where you need help; I can't tell whether you just needed a reminder to use logs, or have forgotten all your algebra!
Thank you. That’s what I needed. Yes I have forgotten all my algebra and I get nervous with logarithmic equations. But now I get it.
I have also realised if I switch axes when plotting my data I get to extrapolate a much more useful equation for my purposes!!

Sazzle

New member
If I understand correctly it is $$\displaystyle y=26e^{0.6x}$$. If that is correct then $$\displaystyle x=\frac{\log(y)-\log(26)}{0.6}$$
Thank you, that is the equation I was trying to rearrange with my shaky algebra skills! Amazing

Harry_the_cat

Senior Member
$$\displaystyle x=\frac{ln(y)-ln(26)}{0.6}$$

Sazzle

New member
$$\displaystyle x=\frac{ln(y)-ln(26)}{0.6}$$
Thank you. Much appreciated