I have bunch of x,y data that at first seem to be fittable with a logarithmic function. My current plot looks like this:
As you can see, the logarithmic fit using
f(x,a,b,c) = a*log(b*x) +c doesn't work for high values of
I didn't know how to make a nice and symmetrical diamond in GIMP using the paths tool, so just imagine the the blue curve is symmetrical and doesn't have a dent in the middle.
So my question is: Is there a typical function for fitting data that looks like this? Fitting one half of a "diamond shape"? I think I remember similar graphs from the fractional distillation of azeotropes, but I couldn't find the exact thing I was looking for.
EDIT: I know the visible points can be fitted well with a quadratic function, but I know due to the chemical background knowledge that it cannot be a simple quadratic. If I use that as a fitting function, the last point will be fitted apporximately as the maximal turning point of the quadratic function. It has to be a diamond shape between 0 and 1. I could try to explain why that is, but it would be difficult...
This is the numerical data I am trying to fit:
#Zn x_applied x_found 0.009 0.02 0.012 0.03 0.016 0.05 0.024 0.07 0.047 0.12 0.069 0.17 0.13 0.24 0.25 0.35