Those dataset are collected by SKetchX (http://sketchx.eecs.qmul.ac.uk/) and PRIS (http://www.pris.net.cn/). For more works about sketches, you can go to http://sketchx.eecs.qmul.ac.uk/
The data format is [\delta x,\delta y, pen state,group id]