# Shiny slider examples with the intrval R package

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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)

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)

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

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