|
 Parametric Curve Fitting question |
| Posted by KarenA on Apr-26-2015 03:34 |
|
I have not yet dug into ChartDirector (I have it through MBS) but I have a question that I
could not find an obvious answer to in the docs...
I want to create calibration curves... And ChartDirector can obviously handle doing the curve
fit and drawing it, and I think getting the equations back...
But to use the calibration curve, I need to get the X data value associated with a specific
experimentally determined Y value. For some curve fit types having only Y= f(x), the math is
non trivial to get X = F(y) (at least over the interval of the data used to get the fit)
Does ChartDirector provide a method to do that? |
| Re: Parametric Curve Fitting question |
| Posted by Peter Kwan on Apr-28-2015 00:40 |
|
Hi KarenA,
ChartDirector can only inform you the parameters for the curve. It cannot solve the
equation X = F(y).
I think for linear, logarithmic, exponential and polynomial of degree 4 or below, the solution
should be easy to compute x given y, as the solution are known and can be found in
mathematics textbook. It would be difficult for polynomials of degree 5 or above, but high
order polynomials are very rarely used in practice, as they are not really suitable for general
curve fitting. If you must use higher order polynomials, you may need to search the internet
on the algorithm to solve polynomial equations. (As far as I know, there is no close formula
for polynomials of degree 5 or above, but numerical approximation methods can be used.)
Regards
Peter Kwan |
|
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