2020/08/30 Realized visualizing data in a given time range. Accelerated the program.
2020/08/29 All program files have been one file draw_map.py. Removed all the hardcoding part. Now users can use command line arguments to input files. For example, python3 draw_map.py gowalla.checkin.
2020/08/27 draw_map_media.py is for datasets in brightkite.checkin's form(brightkite.checkin, gowalla.checkin). draw_map_TSMC2014.py is for datasets in TSMC2014.checkin's form.
2020/08/17 Begin the work. Solve the problem of gradient color.