The premise of your question is a little misleading. The only way to connect two points is with a straight line. Could you clarify what you mean by draw a curve between two points?
This would make sense if you had a collection of several points and you were attempting to draw a smooth curve through these points.
You can use the code you have attached to get an interpolated version.
Alternatively you can use the curve fitting toolbox to get different types of fits for your data as shown below
figure
x_k = [1:2:10]
y_k = [2,8,10,11,22]
plot( x_k, y_k, '+r' ); % plot the original points
n = numel(x_k); % number of original points
xi = interp1( 1:n, x_k, linspace(1, n, 10*n) ); % new sample points
yi = interp1( x_k, y_k, xi );
hold on
plot( xi, yi ); % should be smooth between the original points
hold off
%%Alternatively you can use the curve fitting toolbox to get different fits
figure
f = fit(x_k',y_k','smoothingspline')
plot(f,x_k,y_k)
The following documentation link is a useful starting point for this: http://www.mathworks.com/help/curvefit/fit.html
Another approach for this is to use the polyfit function to fit a polynomial for your dataset as shown in the following doc link: http://www.mathworks.com/help/matlab/ref/polyfit.html
All of these approaches should be a good starting point for you to fit curves to your data.
