# [SciPy-User] technical question: normed exponential fit for data?

Robert Kern robert.kern@gmail....
Thu Mar 24 16:15:34 CDT 2011

On Thu, Mar 24, 2011 at 15:55, Daniel Lepage <dplepage@gmail.com> wrote:
> On Thu, Mar 24, 2011 at 3:59 PM, David Baddeley
>> A really silly question - you are using temperature values in Kelvin (rather
>> than centigrade) aren't you? The chemical/physical assumption is probably that
>> rates are an exponential function of the temperature in Kelvin, not in C. Your
>> high concentration curve is looking awfully like it's heading for an intercept
>> at 0C.
>
> Looks to me like the x-axis goes from 15C to about 28.5C, so the
> intercept is actually around 15C.

It doesn't really matter. If you shift all of the temperature readings
by a constant amount, the shift just gets folded into the coefficient
out in front. The shape of the fitted exponential will look exactly
the same.

c0 * exp(c1*(x+273)) == c0 * exp(c1*273) * exp(c1*x) == c2 * exp(c1*x)

--
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless
enigma that is made terrible by our own mad attempt to interpret it as
though it had an underlying truth."
-- Umberto Eco