How can I implement the depth feature in matlab?

Recently I works on Kinect v2. I read some paper . Most of the papers used depth feature for classification through svm. but i dont understand that how can i implement depth feature in matlab. For example: to use Hog feature there is a built-in function "HOG", similarly have: LDF,LGP,LBP,SIFT etc.But in matlab, is there any built-in function for depth feature? If not then how can i take it as feature from image. I already tried something like: stored the depth value in a array. but how it will work as a feature ? Please help me to reduce the confusion and if any logic need to be applied please instruct. Thanks