Calling additional functions in Shiny

Question

I developed a simple shiny app that take as inputs a score my_x on a distribution with mean my_mean and standard deviation my_sd. As output, the app return a Lattice plot with a Normal Standard distribution with the corresponding z-score of my_x. Please find the code for the app on GitHub.

Now, I would like to add a second functionality to the app:

By checking a checkboxInput I would calculate, for example, the pnorm of the inputs and shade the relative area of the graph.

I wrote the code for the graph (here an example of the expected result), but I cannot figure out how to make it work in Shiny. In particular, I cannot figure how to make the function activated with the checkbox working properly with the first function drawing the graph.

library(lattice)
e4a <- seq(60, 170, length = 10000)
e4b <- dnorm(e4a, 110, 15)
#z-score is calculated with the inputs listed above:

z_score <- (my_x - my_mean)/my_sd

plot_e4d <- xyplot(e4b ~ e4a,
               type = "l",
               main = "Plot 4",
               scales = list(x = list(at = seq(60, 170, 10)), rot = 45),
               panel = function(x,y, ...){
                   panel.xyplot(x,y, ...)
                   panel.abline(v = c(z_score, 110), lty = 2)

                   xx <- c(60, x[x>=60 & x<=z_score], z_score) 
                   yy <- c(0, y[x>=60 & x<=z_score], 0) 
                   panel.polygon(xx,yy, ..., col='red')
               })
print(plot_e4d)

Answer 1

I found a functioning solution. I am pretty sure that it is not the most efficient, but it works. It consists of an if/else statement within the server function calling the plot. I would like to thank @zx8754 for the inspiration.

Here is the ui.r file:

library(shiny)

shinyUI(pageWithSidebar(
headerPanel("Standard Normal"),
sidebarPanel(
    numericInput('mean', 'Your mean', 0),
    numericInput('sd', 'Your standard deviation', 0),
    numericInput('x', 'Your score', 0),
    checkboxInput('p1', label = 'Probability of getting a score smaller than x or z', value = FALSE)
),
mainPanel(
    h3('Standard Normal'),
    plotOutput('sdNorm'),
    h4('Your z-score is:'),
    verbatimTextOutput('z'),
    h4('Your lower tail probability is:'),
    verbatimTextOutput('p1')    
    ))

)

And the server.R file:

library(lattice)

shinyServer(
function(input, output){
    output$sdNorm <- renderPlot({
        dt1 <- seq(-3, 3, length = 1000)
        dt2 <- dnorm(dt1, 0, 1)
        my_mean <- input$mean
        my_sd <- input$sd
        my_x <- input$x
        z <- (my_x - my_mean)/my_sd
        if(input$p1){

            xyplot(dt2 ~ dt1,
                   type = "l",
                   main = "Lower tail probability",
                   panel = function(x,y, ...){
                       panel.xyplot(x,y, ...)
                       panel.abline(v = c(z, 0), lty = 2)
                       xx <- c(-3, x[x>=-3 & x<=z], z) 
                       yy <- c(0, y[x>=-3 & x<=z], 0) 
                       panel.polygon(xx,yy, ..., col='red')
                   })

        }else{
            xyplot(dt2 ~ dt1,
                   type = "l",
                   main = "Standard Normal Distribution",
                   panel = function(x, ...){
                       panel.xyplot(x, ...)
                       panel.abline(v = c(z, 0), lty = 2)
                   })
        }

        })
    output$z = renderPrint({
        my_mean <- input$mean
        my_sd <- input$sd
        my_x <- input$x
        z <- (my_x - my_mean)/my_sd
        z
    })
    output$p1 <- renderPrint({
        if(input$p1){
            my_mean <- input$mean
            my_sd <- input$sd
            my_x <- input$x
            p1 <- 1- pnorm(my_x, my_mean, my_sd)
            p1
        } else {
            p1 <- NULL
        }

    })

}

)