Comparing Iris Species

This Shiny web app takes the “iris” data set in R and displays the relationship between sepal length and width for a species designated by the user. The data contains information on 3 species: setosa, versicolor, and virginica. A summary of the relevant variables for all species types is shown below.

data(iris)
summary(iris$Sepal.Length)

   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
  4.300   5.100   5.800   5.843   6.400   7.900 

summary(iris$Sepal.Width)

   Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
  2.000   2.800   3.000   3.057   3.300   4.400 

The ui.R code shows that the user is prompted to make two choices that generate reactive output in a scatter plot.

• A dropdown list with each iris species
• A checkbox indicating whether a trendline should be displayed

library(shiny)

shinyUI(pageWithSidebar(
  headerPanel("Comparing Iris Species"),
  sidebarPanel(
    selectInput("variable","Select a Species:",
                list("setosa" = "setosa", 
                     "versicolor" = "versicolor",
                     "virginica" = "virginica",
                     "all species" = "all species")),
    checkboxInput("trendline","Show trendline",value=TRUE)
  ),
    mainPanel(
      h3('Sepal Length and Width'),
      plotOutput("irisPlot")
    )
  ))

The server.R code generates a graph of sepal length vs. sepal width for the species specified by the user in input$variable, and generates one of two graphs depending whether the user selects to add a trendline.

shinyServer(
  function(input,output){
    formulaText <- reactive(function(){
    paste("Sepal.Length ~", input$variable)  
    })
    output$caption <- reactiveText(function() {
    formulaText()
    })
       output$irisPlot <- reactivePlot(function() {
     if (input$variable == "setosa") {
       iris_data <- iris[iris$Species=="setosa",]
       col = "#999999" 
     } 
     else if (input$variable == "versicolor") {
       iris_data <- iris[iris$Species=="versicolor",]
       col="#E69F00"
     }
     else if (input$variable == "virginica") {
       iris_data <- iris[iris$Species=="virginica",]
       col="#56B4E9"
     }
     else if (input$variable == "all species") {
       iris_data <- iris
       col=c("#999999", "#E69F00", "#56B4E9")
     }
     p <- ggplot(iris_data, aes(Sepal.Length,Sepal.Width)) + geom_point(aes(color=Species)) + scale_color_manual(values=col)  + coord_cartesian(ylim=c(2,4.5),xlim=c(4,8)) + theme(legend.position="top") + geom_smooth(method="lm",color="black")
     p2 <- ggplot(iris_data, aes(Sepal.Length,Sepal.Width)) + geom_point(aes(color=Species)) + scale_color_manual(values=col)  + coord_cartesian(ylim=c(2,4.5),xlim=c(4,8)) + theme(legend.position="top") 
     ifelse(input$trendline,print(p),print(p2))
   })
})