Thread Subject: extrapolation a function

Hello to everyone, I have this problem:

Suppose the following data comes from an exponentially decreasing phenomena, for example, discharge on a capacitor.

When will the the charge be half the charge at time t = 0?

(-1.5, 1.11), (-0.9, 0.92), (-0.7, 0.85), (0.7, 0.57), (1.2, 0.49), (1.4, 0.45)

With Matlab I can get the exponential function fit better these experimental data with cftool, not problem with it, but how can get the completelly fit to 0, I need for that an extrapolation function...any help?

The trick adding (0.0,00) as a last point can help,, but I want to know if there exist dome extrapolation function for it.

Thnaks in advance.

"Jose " <jose.l.vega@gmail.com> wrote in message <i5uhip$1td$1@fred.mathworks.com>...
> Hello to everyone, I have this problem:
>
> Suppose the following data comes from an exponentially decreasing phenomena, for example, discharge on a capacitor.
>
> When will the the charge be half the charge at time t = 0?
>
> (-1.5, 1.11), (-0.9, 0.92), (-0.7, 0.85), (0.7, 0.57), (1.2, 0.49), (1.4, 0.45)
>
> With Matlab I can get the exponential function fit better these experimental data with cftool, not problem with it, but how can get the completelly fit to 0, I need for that an extrapolation function...any help?
>
> The trick adding (0.0,00) as a last point can help,, but I want to know if there exist dome extrapolation function for it.
>
> Thnaks in advance.

ok, guys, it works perfectly with the trick (1.10,0.0), and using a smoothing spline. Thanks.