renderimag.R

library(shiny)

ui <- pageWithSidebar(
  headerPanel("renderImage example"),
  sidebarPanel(
    sliderInput("obs", "Number of observations:",
                min = 0, max = 1000,  value = 500)
  ),
  mainPanel(
    # Use imageOutput to place the image on the page
    imageOutput("myImage")
  )
)

server <- function(input, output, session) {
  output$myImage <- renderImage({
    # A temp file to save the output.
    # This file will be removed later by renderImage
    outfile <- tempfile(fileext = '.png')
    
    # Generate the PNG
    png(outfile, width = 400, height = 300)
    hist(rnorm(input$obs), main = "Generated in renderImage()")
    dev.off()
    
    # Return a list containing the filename
    list(src = outfile,
         contentType = 'image/png',
         width = 400,
         height = 300,
         alt = "This is alternate text")
  }, deleteFile = TRUE)
}

shinyApp(ui, server)