...
...and the corresponding velocity data points - note the zero value in the middle: 
These jumps in velocity values result in acceleration values that oscillate from negative to positive to negative and so on. We need a smoother graph of acceleration.
A possible solution is to use MATLAB to write a new data file that uses every third point from the original data in order to eliminate redundancyEDIT: This redundancy problem is easily solved by changing the frame step size to 2 or 3 (located to the right of the frame slider, underneath the video display).