I have a 2D histogram which I plot as a color map, color is the quantity, horizontal axis is frequency and the vertical axis is the time. Now I see that in this color map, the quantity is changing position in a parabolic shape, so I like to fit a parabola on top of it, as a function of time and frequency.

I have done many fits with ROOT, but this is my first time trying to fit on a 2D histogram, basically not sure how to do it. Any hint, or example, is appreciated.

*ROOT Version:* 6.22/06

*Platform:* osx

*Compiler:* PyROOT