How can I curve fit this diffusion equation?

I am plotting the following points

%t is the time points

t=[0 300 600 1800 3600 7200 10800 14400 18000 21600 25200 36000 43200 86400 108000 129600];

%C1 is the X-RAY attenuation

C1=[0 3.4118 5.015 8.3483 14.5637 23.4199 30.2665 35.5957 40.3528 43.7849 47.6186 54.3443 58.3553 69.2554 70.6798 72.0403];

To curve fit those points I am using the following function

clearfunction C1=Conc(t,D)

C1=0;

z=2; %Contact interface cartilage-bath

h=2; %Cartilage height

%D is the diffusion coefficient that we are looking for

%t corresponds to the different time points

for i=1:1000

C=(((-1)^i)/(2*i-1))*(cos((i-0.5)pi(-0.5)))*(exp(-((i-0.5)^2)pi^2)(D/4)*t);

C1=C1+C;

end

C1=1+(4/pi)*C1

end

Where the unknown we want to find is D .

The curve I obtain by plotting the points is not being correctly fitted by the function I am using. Any ideas would be appreciated!

[Ahmet Cecen]

This is too jargony and compacted for me. Write it down in the following fashion:

I have samples X and observations Y and I wanna fit THIS formula (a function of X).

Basically share what the actual problem you are trying to solve is as well, not just how you tried to solve it.