How to draw a curve along the mouth with the obtained corner points?

I got an error while drawing a curve for the obtained corner points of the mouth. I used vision.CornerDetector and step commands to obtains the points, but i couldn't draw the curve using polyfit and polyval commands.The set of steps I have written is :

cornerDetector = vision.CornerDetector('Method', 'Minimum eigenvalue (Shi & Tomasi)');

points = step(cornerDetector, rgb2gray(mouthcrop));

P = polyfit(points(:,1),points(:,2),2);

Y = polyval(P,points(:,1));

plot(points(:,1),Y,'b','linewidth',2,'markersize',10)

The error that is displayed:

Undefined function 'qr' for input arguments of type 'uint32'

Error in polyfit (line 66)

[Q,R] = qr(V,0);

Answer 1

[Image Analyst]

Read this http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup then fix your post. Also, you forgot to post an image so I really don't know how to help you since I can't visualize it. About the only thing I can think of is John D'Errico's interparc: http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A679 but we might have better solutions if we knew what you were dealing with.