curve fitting open fast data

[lt72884]

I have been using pydatview to view the results of open fast such as the image below of a RootFxb1 parameter.

https://photos.app.goo.gl/dPpastXHC8L8pzWD8

I discovered the curve fitting option under tools. I used the sin wave function but the curve is not that great of a fit. Is there a better way to do this? or a way to change the settings of the curve fit in pydat view? The R^2 value is very very low. However, on some parameters, the graph is not to bad. Is there another way to curve fit it with another software maybe or somehow curve fit it better in pydatview?

https://photos.app.goo.gl/3RYUgXMYA7Bi2emQ6

thanks