How to get equation from each plot?

So I have this code:

wkt is 117*1 array

x is also 117*1 array

a=polyfit(wkt,x);
b=polyval(a,wkt);
figure
plot (wkt,x)
hold on
plot (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.

Answer 1

[Walter Roberson]

https://www.mathworks.com/help/matlab/ref/polyint.html polyint will integrate directly from the polynomial coefficients.

[Okinawa Rikenata]

Ahh thankyou so much!!