Your points are no tin an order....first make them into an order using boundary.
load data1.mat ;
x = data1(:,1) ; y = data1(:,2) ;
idx = boundary(x,y) ;
x = x(idx) ; y(idx) ;
plot(x,y)
Hope the above one works, if you are okay with the above, you have your data into a polygon.
If not, you can have a look on, Beizer Curve. https://in.mathworks.com/matlabcentral/fileexchange/33828-generalised-bezier-curve-matlab-code
