ggplot2 - facet和独立的y轴计算。

I am a relative R / ggplot2 beginner and I looking to create the following plot below so that the y axis is calculated independently for each facet. For instance, I would like Time Period 1 percentages on the y axis to just be calculated by the data faceted by time period1, and the Time Period 2 percentages to be calculated by the data faceted by time period 2. I am a relative R / ggplot2 beginner and I look