Péter Sólymos

Shiny slider examples with the intrval R package

March 08, 2018 Code R intrval shiny slider

The intrval R package is lightweight (~11K), standalone (apart from importing from graphics, has exactly 0 non-base dependency), and it has a very narrow scope: it implements relational operators for intervals — very well aligned with the tiny manifesto. In this post we will explore the use of the package in two shiny apps with sliders.

The first example uses a regular slider that returns a single value. To make that an interval, we will use standard deviation (SD, sigma) in a quality control chart (QCC). The code is based on the pistonrings data set from the qcc package. The Shewhart chart sets 3 sigma limit to indicate state of control. The slider is used to adjusts the sigma limit and the GIF below plays is as an animation.

library(shiny)
library(intrval)
library(qcc)

data(pistonrings)
mu <- mean(pistonrings$diameter[pistonrings$trial])
SD <- sd(pistonrings$diameter[pistonrings$trial])
x <- pistonrings$diameter[!pistonrings$trial]

## UI function
ui <- fluidPage(
  plotOutput("plot"),
  sliderInput("x", "x SD:",
    min=0, max=5, value=0, step=0.1,
    animate=animationOptions(100)
  )
)

# Server logic
server <- function(input, output) {
  output$plot <- renderPlot({
    Main <- paste("Shewhart quality control chart",
        "diameter of piston rings", sprintf("+/- %.1f SD", input$x),
        sep="\n")
    iv <- mu + input$x * c(-SD, SD)
    plot(x, pch = 19, col = x %)(% iv +1, type = "b",
        ylim = mu + 5 * c(-SD, SD), main = Main)
    abline(h = mu)
    abline(h = iv, lty = 2)
  })
}

## Run shiny app
if (interactive()) shinyApp(ui, server)

regular slider

The second example uses range slider returning two values, which is our interval. To spice things up a bit, we combine intervals on two axes to color some random points. The next range slider defines a distance interval and colors the random points inside the ring.

library(shiny)
library(intrval)

set.seed(1)
n <- 10^4
x <- round(runif(n, -2, 2), 2)
y <- round(runif(n, -2, 2), 2)
d <- round(sqrt(x^2 + y^2), 2)

## UI function
ui <- fluidPage(
  titlePanel("intrval example with shiny"),
  sidebarLayout(
    sidebarPanel(
      sliderInput("bb_x", "x value:",
        min=min(x), max=max(x), value=range(x),
        step=round(diff(range(x))/20, 1), animate=TRUE
      ),
      sliderInput("bb_y", "y value:",
        min = min(y), max = max(y), value = range(y),
        step=round(diff(range(y))/20, 1), animate=TRUE
      ),
      sliderInput("bb_d", "radial distance:",
        min = 0, max = max(d), value = c(0, max(d)/2),
        step=round(max(d)/20, 1), animate=TRUE
      )
    ),
    mainPanel(
      plotOutput("plot")
    )
  )
)

# Server logic
server <- function(input, output) {
  output$plot <- renderPlot({
    iv1 <- x %[]% input$bb_x & y %[]% input$bb_y
    iv2 <- x %[]% input$bb_y & y %[]% input$bb_x
    iv3 <- d %()% input$bb_d
    op <- par(mfrow=c(1,2))
    plot(x, y, pch = 19, cex = 0.25, col = iv1 + iv2 + 3,
        main = "Intersecting bounding boxes")
    plot(x, y, pch = 19, cex = 0.25, col = iv3 + 1,
         main = "Deck the halls:\ndistance range from center")  
    par(op)
  })
}

## Run shiny app
if (interactive()) shinyApp(ui, server)

range slider

If you think there are other use cases for intrval in shiny applications, let me know in the comments section!

If you want to learn more about how to host Shiny apps, check out the Hosting Data Apps website!

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CalgaryR & YEGRUG Meetup: Data Cloning - Hierarchical Models Made Easy

I moved to Canada in 2008 to start a postdoctoral fellowship with Prof. Subhash Lele at the stats department of the University of Alberta. Subhash at the time just published a paper about a statistical technique called data cloning. Data cloning is a way to use Bayesian MCMC algorithms to do frequentist inference. Yes, you read that right.

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