我为什么会出错:在rapp中找不到函数multiplot ?

I am trying to make a tab of my R shiny app display multiple plots using the ggplot2 multiplot() function. All the other libraries I use are in my global.R, but the ggplot2 library is definitely imported, so I don't understand why I get this error:I am trying to make a tab of my R shiny app dis