ggplot:在传递因子为参数时绘制单独的y线

I want to create the following plot: The x-axis goes from 1 to 900 representing trial numbers. The y-axis shows three different lines with the moving average of reaction time. One line is shown for each difficulty level (Hard, Medium, Easy). Separate plots should be shown for each participant using facet_wrap. I want to create the following plot: The x-axis