# MATLAB: How to get equation from each plot

equationplot

So I have this code:
wkt is 117*1 array
x is also 117*1 array
a=polyfit(wkt,x);b=polyval(a,wkt);figureplot (wkt,x)hold onplot (wkt,b)
Then I get a figure with 2 different plots. My problem is how to get the equation for each plot so I can evaluate the area between 2 curves. If I use this
a=trapz(wkt,x)-trapz(wkt,b)
will I get a correct result? Or is there another way? Thank you.