To accurately fit a curve to my data using a fitting function, I need to follow a structured approach. The current fitting curve is incorrect, so how should I proceed to achieve a correct fit?
Here is my code:

I collected data with a spectrometer and I am now trying to fit a Planck curve onto my data. For some reason I don’t seem to get it to work. I think it has something to do with the scale of my intensity but I don’t know how to fix that.

So I am trying to fit a 2-dimensional function with polynomials.

I have some decay data that looks like it could be biexponential so I want to fit it to the equation of y(t) = y0 + a1e^(-k1t) + a2e^(-k2t), while fitting the parameters of y0, a1, k1, a2, and k2. I can get a decent fit, but based on the physical system I am analyzing the parameters of y0, a1, and a2 should sum together to equal 1, with all three being positive values. Is there a way I can do this?