how to detect nose in matlab

vid = imaq.VideoDevice('winvideo', 1, 'YUY2_640x480','ROI',[1 1 640 480]);
videoFrame = step(vid);
bbox            = step(faceDetector, videoFrame);
noseDetector = vision.CascadeObjectDetector('Nose');
faceImage    = imcrop(videoFrame,bbox(1,:));
noseBBox     = step(noseDetector,faceImage);
noseBBox(1,1:2) = noseBBox(1,1:2) + bbox(1,1:2);
tracker = vision.HistogramBasedTracker;
initializeObject(tracker, hueChannel, noseBBox(1,:));

% Create a video player object for displaying video frames.
ROI = get(vid,'ROI');
videoSize = [ROI(3) ROI(4)];
videoPlayer  = vision.VideoPlayer('Position',[300 300 videoSize(1:2)+30]);