Showing the results in the result tab of Shiny

Question

How can I output the results of a function (say confusionMatrix from caret package) on the result tab of the mainPanel in Shiny?

Here's what I have in server.R:

  #Create Confusion Matrix of Predictions
  ref = matrix(c("P", "N", "P", "P", "P", "P","N"), ncol=1)
  pred = matrix(c("P", "N", "N", "P", "P", "P","P"), ncol=1)
  output$confusionMat <- renderPrint({
    confusionMatrix(ref,pred)
  })

And here's what I have in ui.R:

 mainPanel(width = 4,
      tabsetPanel(
        #tabPanel("Plot", plotOutput("plot")),
        tabPanel("Result", selectInput("featureEx", "Feature Exploration",
                                       c("ABC", "AB", "AC", "A"), multiple = TRUE),
                          helpText("Prediction Results Using Testing data"),
                          dataTableOutput("confusionMat"),
                          capture.output("confusionMat"),
                          plotOutput("fePlot")
                         ),

When I enter the function in RStudio here's the result I get:

> confusionMatrix(ref,pred)
Confusion Matrix and Statistics

          Reference
Prediction N P
         N 1 1
         P 1 4

               Accuracy : 0.7143          
                 95% CI : (0.2904, 0.9633)
    No Information Rate : 0.7143          
    P-Value [Acc > NIR] : 0.6792          

                  Kappa : 0.3             
 Mcnemar's Test P-Value : 1.0000          

            Sensitivity : 0.5000          
            Specificity : 0.8000          
         Pos Pred Value : 0.5000          
         Neg Pred Value : 0.8000          
             Prevalence : 0.2857          
         Detection Rate : 0.1429          
   Detection Prevalence : 0.2857          
      Balanced Accuracy : 0.6500          

       'Positive' Class : N

So I would like to show the confusion table in a nicely formatted matrix in shiny and I was hoping to be able to do so using outputTable which doesn't show anything and also show the plain text as well in the result tab. Currently nothing is shown in the mainPanel. Any solution?

Can I make a suggestion and ask you to provide a single-file shiny going forward so we can easily run the code and view the results? I'm going to offer a solution but it won't be reproducible because you haven't provided the full code — Bahae Omid

Bahae Omid Bahae Omid · Accepted Answer · 2015-03-04T05:23:36

capture.output, from the base package, coupled with textplot from the PerformanceAnalytics package may interest you in this case.

capture.output lets you extract every single element from the output of confusionMatrix separately in text format. Note that you may re-arrange the output of capture.output however you want but in this particular example I'm not going to modify the output. Then you will have to pass the output of capture.output to textplot in order to be able to render the output as a plot in Shiny.

In the example you provided above, instead of renderPrint I would use renderPlot and utilize the two functions mentioned above as follows:

require(PerformanceAnalytics)
output$confusionMat <- renderPlot({   #Replaced renderPrint with renderPlot
    textplot(      #wrap textplot around capture.output
        capture.output(     #capture output of confusionMatrix in text format
            confusionMatrix(ref,pred)  #your original code here
        )      #close capture.output
    )    #close textplot

}) #close renderPlot

But if you REALLY want to use renderDataTable you will need to make sure that you pass a dataframe to renderDataTable.

Here's a fully reporducible example with a different data set. If you run the code below, the results will look ugly and that's because I did not take the time to re-arrange the output of capture.output to my liking. If you want to use renderDataTable you will need to spend some time to change the layout of the dataframe being passed to renderDataTable:

require(shiny)
require(caret)
require(PerformanceAnalytics)

server <- function(input,output,session){
    output$confusionMat <- renderDataTable({
        data.frame(
            capture.output(
                confusionMatrix(iris$Species, sample(iris$Species))
            )
        )

    })

}

ui <- shinyUI(fluidPage(

    sidebarLayout(
        sidebarPanel(

        ),

        mainPanel(
            dataTableOutput('confusionMat')
        )      

    )
))

shinyApp(ui = ui, server = server)

Showing the results in the result tab of Shiny

2 Answers