Originally posted by joe shmoThat is a hard equation to solve!
I'm trying to curve fit 3 data points. The system has the characteristics of the general function:
Y(x) = C*(1-e^(-b*x))
I have 3 ordered pairs (0,0),(y1,x1),(y2,x2).
I can solve for the undetermined constants (C & b) numerically from;
y_1 = C*(1-e^(-b*x_1))
y_2 = C*(1-e^(-b*x_2))
The solution (0,0) is naturally a consequence of the eq ...[text shortened]... s (0,0) and (x_1,y_1), but falls short on matching (x_2,y_2). What is the explanation for this?
Originally posted by iamatigerThere were actual numbers (I didn't solve it generally) I used a spreadsheet.
That is a hard equation to solve!
how did you do it?!
Originally posted by iamatigerSure,
Any chance of your initial numbers? It is an interesting conundrum, but I think the solution does depend quite strongly on the numbers because of the powers (and can the values be complex numbers, by the way?)
Originally posted by joe shmoAs x approaches infinity, y will approach C because it will be y=C*(1-0). That should be a maximum. Therefore your C cannot equal 4201.78 while your y equals 4250 in the third point. You need a C that is greater than 4250.
The solution for "b" I found was between 0.26 - 0.27, C = 4201.78
If you mean the values of the constants being imaginary, I would say probably not.
Originally posted by iamatigerNo... I re-checked my equation, and found I flipped some signs being sloppy with the algebra...oddly enough the solution to the wrong equation was somewhat close to the proper equations solution!
looking at what you said again, I don't suppose you wrote b down wrongly Joe?
b is between 0.2[b]46 and 0.247 ....[/b]