I need to fit my data in Origin, which shows biphasic response, and I've got an equation that is studied to fit for the biphasic nature of my data. This is the equation I'm looking for a way to use [double z = (x-xc)/w; y = y0+A*exp(-exp(-z)-z+1)]. I'm clueless how to determine the initial values for the parameters and set the upper and lower bounds to make the fit converge.

I've attached a picture of a scatter plot of my data (response vs. concentration), and I need to fit this plot in Origin.

I appreciate your kind help to get me understand doing this.

Thank you very much

Regards

Nirujan