如何在Shiny应用程序中使用ggplot创建反应图

To whom can help, this is my first post. I have spent several hours trying to figure out how to generate a bar plot using ggplot for a shiny app I want to create. The ui works find, however; the server function generates an empty plot. The issue is with renderPlot function. I believe I must not be passing the reactive values properly to the aes_string arguments in ggplot. C2 is a filtered dataset. The goal is to build a simple app in which the user selects a two variables, a dataset is filtered based upon those variables. The subsetted dataset is passed to ggplot data argument.To whom can help, this is my first post. I have