Im im trying to validate my engineering work using Matlab. I have a series of x and y data that I have plotted on a Log-Log Graph. 

The result is a curve. 

What I need to do is to apply a curve fit to this graph, and show what the equation of the fit is? 

I have tried other answers on here and tried using polyfit and polyval but they aren't really doing what I need but what I lack is the forthwith understanding. 

Kind regards