Control chart for the weekly total number of detected viruses (Beijing).

<p>It's an example to illustrate the peak performance analysis method. The horizontal ordinate denotes the corresponding number of the 159 monitoring weeks in chronological order. As an example, the 13th week in 2006 is numbered as 1. The black line is the time series of virological data in Beijing. The green lines are the annual medians, and the red lines are the annual 2 control limits, that is, the thresholds. More information about the results of this method is given in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0058434#pone.0058434.s001" target="_blank">Table S1</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0058434#pone.0058434.s002" target="_blank">S2</a> in detail.