Not quite...
Ok so say the first row of x and v are [x1,x2...xN] and [v1,v2...vN] respectively. What MATLAB does is at t=0 plot x against v but only as points, not as a curve. At t=1, it plots the second row, again as points, but now joins (x1,v1) from row one, with the (x1,v1) from row two...