title: Creating dataset index from unique combinations of columns in Matlab
body: <p>I have a dataset stored as a numeric matrix. The first 4 columns uniquely identify a "case". Each case is a procedure performed in a patient in a hospital on a certain date. So, the first column is hospital id, 2nd column is patient id, 3rd column is date, and 4th column is procedure type. What is the easiest way to assign a single column unique id based on unique combinations of the 4 columns. Thanks!</p>