Shiny :: nonstandard evaluation

 http://www.alshum.com/nse/

Ex1 >

> library(ISLR)
> library("ISLR")

> aaa <- "ISLR"
> library(aaa)
Error in library(aaa) : there is no package called ‘aaa’ 

Ex2>  ggplot 

p <- ggplot(mtcars, aes(c(input$sel, mpg, colors=as.factor(cyl))) +
    geom_point()
print(p)

이유는 그냥 ggplot 을 사용했기 때문

Warning: Error in renderPlot: object 'cyl' not found
ERROR: Unknown input:tbl_df
Don't know how to automatically pick scale for object of type ...
Warning: Error in : Aesthetics must be either length 1 or the same as the data (11): x, y

Shiny내에서 ggplot 사용방법

library(shiny)
library(ggplot2)

ui <- fluidPage(
    titlePanel("simple"),
    selectInput("sel", "select:", choices = c("wt","hp", "disp")),
    plotOutput("simpleplot"))

server <- function(input, output, session){
    output$simpleplot<- renderPlot({
        mtcars$cyl <- as.factor(mtcars$cyl)
        p <- ggplot(mtcars) + aes_string(input$sel, "mpg", colors="cyl") +
             geom_point()
        print(p)
    })
}

shinyApp(ui,server)

Shiny에서 쓰이는 함수

• switch() 
• get() : Object 찾기
• assign() : object를 다른 이름으로 저장