R - shiny package- sending plot to shiny

Question

I am going to build a web page that clusters iris data based on the number of clusters the user enters. It uses K means algorithm to cluster the data and shows a plot of clustered data. It does not work and I do not know why. I started from this link: http://rstudio.github.io/shiny/tutorial/#sending-images

Here are my files: ui.R

    library(shiny)

shinyUI(pageWithSidebar(
  headerPanel("Clustering iris Data"),
  sidebarPanel(
    sliderInput("k", "Number of clusters:",
                min = 1, max = 5,  value = 3)
  ),
  mainPanel(
    # Use imageOutput to place the image on the page
    imageOutput("myImage")
  )
))

and server.R

library(shiny)
library(caret)
library(ggplot2)
data(iris)

inTrain  <- createDataPartition(y=iris$Species, p=0.7, list=FALSE)
training <- iris[inTrain,]
testing  <- iris[-inTrain,]

shinyServer(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')


    kMeans1 <- kmeans(subset(training,select=-c(Species)),centers=input$k)
    training$clusters <- as.factor(kMeans1$cluster)

    # Generate the PNG
    png(outfile, width=400, height=600)
    qplot(Petal.Width,Petal.Length,colour=clusters,data=training,main="iris Data Clusters")
    print(qplot)
    #plot(training$Petal.Width,training$Petal.Length,colour=clusters,data=training,main="iris Data Clusters")
    #hist(rnorm(input$k), main="Generated in renderImage()")
    #myImage

    dev.off()


    # Return a list containing the filename
    list(src = outfile,
         contentType = 'image/png',
         width = 400,
         height = 600,
         alt = "This is alternate text")
  }, deleteFile = TRUE)

})

Answer 1

I think you just have to change

qplot(Petal.Width,Petal.Length,colour=clusters,data=training,main="iris Data Clusters")
print(qplot)

to something like this:

qP <- qplot(
      Petal.Width,Petal.Length,
      colour=clusters,data=training,
      main="iris Data Clusters")
    print(qP)

Because your call to qplot() was not actually creating an object; which is why print(qplot) was printing the function definition of qplot in the console.