select a variable from drop-down and pass it as an argument in reactivePlot in R Shiny

Question

I have a general question about R Shiny application: I have a list of IDs that end-users can choose from in a drop-down menu (selectInput), and I hope to make a corresponding plot based on this ID. In other words, the selected variable will be passed as an argument in the plot function, and each time I choose a different ID, the plot is also changed. Can I know if this is doable in Shiny? I appreciate if anyone can provide a working example on similar problems. Thank you!

Answer 1

Here is a sample working example with dropdown as an argument. The output of this program can be viewed on http://glimmer.rstudio.com/bishwamitrad/ggplot2browser/ :

ui.R

library(shiny)
library(ggplot2)

## Define UI for miles per gallon application

dataset <- diamonds

title <- "Diamonds data Analysis"

## Define UI for application that plots random distributions

shinyUI(pageWithSidebar(

  ## Application title
  headerPanel(title),

  ## Sidebar with a slider input for number of observations

  sidebarPanel (

    sliderInput('sampleSize','Sample Size', min=1, max=nrow(dataset),
                value=min(1000,nrow(dataset)),
                step=500,
                round=0),

    selectInput('x','X',names(dataset)),
    selectInput('y','Y',names(dataset),
                names(dataset)[[2]]),

    selectInput('color','Color',c('None',names(dataset))),

    selectInput('shape','Shape',c('None',names(dataset))),

    checkboxInput('jitter','Jitter'),
    checkboxInput('smooth','Smooth'),

    selectInput('facet_col','Facet Column',
                c(None='.',names(dataset))),

    selectInput('facet_row','Facet Row',
                c(None='.',names(dataset)))

  ),

  ## Show a plot of the generated distribution

  mainPanel(plotOutput('plot',height="700px"))


)

)

server.R

library(shiny)
library(ggplot2)

## Define server logic required to generate and plot a random distribution
shinyServer(function(input,output) {

  dataset <- reactive(function(){
    diamonds[sample(nrow(diamonds),input$sampleSize),]
  })

output$plot <- renderPlot(function(){

  p <- ggplot(dataset(),aes_string(x=input$x, y=input$y))+geom_point()

  if(input$color != 'None')
    p <- p + aes_string(color=input$color)

  if (input$shape != 'None')
    p <- p + aes_string(shape=input$shape)

  facets <- paste(input$facet_row, '~', input$facet_col)

  if (facets != '. ~ .')
    p <- p + facet_grid(facets)

  if (input$jitter)
    p <- p + geom_jitter()

  if (input$smooth)
    p <- p + geom_smooth()


  print(p)

})


})