How do I form an equation for the ff data?

Hello all,

I want to come up with an equation [something like C = f(S)] relating between the variables involved.

My data:

S--------C
0--------6.4
9--------7.81
100-----10.9
1000----27.9
2000----29.42

Any help pls..

*brain explodes!*

Do you have a graphing calculator or microsoft excel?

Yes, I do have an excel. But what tool will i used to formulate the formula?

First you plot the list you have in excel. Then, there's an option the graph window that you just click, and the forumula will appear on the graph, I can't exatly remember which part of the graph you right click on though.

now i want to know to because the only tool i know of in excel is the one that does best fit lines and it doesnt match what the fxn should be exactly.

well, there are different types of line equations you can formate from it. linear regresion, quadratic, etc. you just have to pick the right one.

yea i tried all of them they dont match up to his graph at all.

Then, chances are you've got something entered wrong by mistake, or your data points aren't very precise. I really don't know what else to tell you.

I can't find the option in Excel that iliterate_enginere is talking about.

But using the graph in Excel, i tried these:
1. linear regression (but eliminated the error function):
C = 0.02069S + 7
(This is valid only for S = 0 to 800, large error for
larger S.)
2. Second approach for approx.
C = C0 + Cf[1-e^(kS)], and came up with
C = 7 + 23[1-e^(-0.00194S)]

The second is giving me close proximities with the values given in the table.

Does anyone has better and accurate derived equation?