I have encountered a problem and would like to ask everyone to help solve it. The problem to be solved is how to close the following two fitted curves. Thank you very much for your enthusiastic answers.

My code:

load dataA.mat
%x1=dataA(:,1);
%y1=dataA(:,2);
f1 = fit(xAbove,yAbove,'smoothingspline','SmoothingParam',0.0001);%smoothingspline
%plot(f1,xAbove,yAbove)
plot(f1,'-r')
hold on
load dataB.mat
%x2=dataB(:,1);
%y2=dataB(:,2);
[xx,ind] = sort(xBelow);
yy2 = smooth(xBelow,yBelow,0.5,'rloess');
yy=yy2(ind);
xAbove(1)==xx(1);
yAbove(1)==yy(1);
plot(xx,yy,'r-')

Answer 1

[KSSV]

load dataA.mat
%x1=dataA(:,1);
%y1=dataA(:,2);
f1 = fit(xAbove,yAbove,'smoothingspline','SmoothingParam',0.0001);%smoothingspline
%plot(f1,xAbove,yAbove)
% plot(f1,'-r')
xx1 = xAbove ;
yy1 = f1(xx1) ; 
hold on
load dataB.mat
%x2=dataB(:,1);
%y2=dataB(:,2);
[xx,ind] = sort(xBelow);
yy2 = smooth(xBelow,yBelow,0.5,'rloess');
yy=yy2(ind);
xAbove(1)=xx(1);
yAbove(1)=yy(1);

xx = [xx1 ; flipud(xx) ; xx1(1)] ;
yy = [yy1 ; flipud(yy); yy1(1)] ; 
plot(xx,yy,'r-')