error message : Index exceeds matrix dimensions

 load('callast.mat');

 vid = videoinput('macvideo', 1, 'YCbCr422_1280x960');%left
 vid2 = videoinput('macvideo', 2, 'YCbCr422_1280x960');%right

 I1 = getsnapshot(vid);
 I2 = getsnapshot(vid2);

 faceDetector = vision.CascadeObjectDetector;
 face1 = faceDetector(I1);
 face2 = faceDetector(I2);

 center1 = face1(1:2) + face1(3:4)/2;
 center2 = face2(1:2) + face2(3:4)/2;

 point3d = triangulate(center1, center2, stereoParams);
 distanceInMeters = norm(point3d)/1000;

 distanceAsString = sprintf('%0.2f meters', distanceInMeters);
 I1 = insertObjectAnnotation(I1,'rectangle',face1,distanceAsString,'FontSize',18);
 I2 = insertObjectAnnotation(I2,'rectangle',face2, distanceAsString,'FontSize',18);
 I1 = insertShape(I1,'FilledRectangle',face1);
 I2 = insertShape(I2,'FilledRectangle',face2);

 imshowpair(I1, I2, 'montage');

i am trying to acquire images from stereo-cameras and detect faces with distance and i keep getting this error ...

Index exceeds matrix dimensions.

Error in lllss (line 20) center1 = face1(1:2) + face1(3:4)/2;

Answer 1

[Image Analyst]

Well clearly face1 does not have 4 elements like you assumed. Use normal debugging procedures to find out what it is. It might even be null/empty.