caitlin - if your movements are in a matrix, say nx2, where each row is a coordinate for the movement, then the number of movements is equivalent to the number of rows
movementCoodinates = ...; % your coordinates
numberOfCoordinates = size(movementCoodinates, 1);
Can your data be put in this (or a similar format)? Else, if you just have a row array (like your example above of [3 4 2 5]), then the number of movements is just the number of columns divided by two
movementCoodinates = ...; % your coordinates
numberOfCoordinates = size(movementCoodinates, 2) / 2;
