A short tale of... data vizes

4 minutes read
Data Visualization • Analytics
data visualization • rstats • shiny • tableau

A short tale of… data vizes. It’s about Tableau, R, and Shiny. How to prepare/build an existing and well-known Tableau visualization with R and provide web analysis interactivity. Will be using the raw data from the sample workbook named “Regional” that comes with Tableau Desktop. The following image below is a snapshot of the visualization that we will try to reproduce with R. You can also view and interact with this visualization on my Tableau Public profile page -> http://tabsoft.co/22IOMjD

Tableau_SATScore

Let’s start by recreating the same visualization (static) with R. Open RStudio, copy and paste the following R code and run it.

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library(dplyr)
library(ggplot2)

# Read CSV data
sat_score = read.csv("/Data/TableauDataSet_Education.csv")
sat_score$Total.Score <- as.numeric(as.character(sub(",", "", sat_score$Total.Score)))

# Group by
by_college <- group_by(sat_score, College, Total.Score)

# Summarize
college_score <- summarise(by_college , NumberOfStudents = n())

# Plot
ggplot(college_score, aes(Total.Score, NumberOfStudents)) + geom_point(alpha=.8, size=4.5, aes(color=College)) + 
  scale_y_continuous(breaks=seq(0, 300, 50)) +
  scale_x_continuous(breaks=seq(900, 2300, 100)) +
  geom_vline(aes(xintercept=mean(Total.Score, na.rm=TRUE)), color="grey", linetype="dashed", size=1) + 
  geom_text(aes(x=mean(Total.Score, na.rm=TRUE), y=max(NumberOfStudents) + 10, label=paste("Avg Score ", round(mean(Total.Score, na.rm=TRUE)), sep="")), hjust = .5, size = 5, colour = "black", family=c("Arial")) +
  xlab("SAT Score") + ylab("Number of Students") +
  scale_color_manual(values=c("#4E92C1", "#FF9C44", "#5BB55B", "#DF5758", "#AC89CC", "#A67C73", "#E995D0", "#9C9C9C")) +
  theme_bw() +
  theme(legend.key=element_blank())

The output will produce the following, a nice simple static plot… of course with no interactivity!

Rplot01

Then comes Shiny by RStudio which is a web application framework for R that turns your analyses into interactive web applications. Check out the Getting Started Guide for all the details.

Shiny apps have two important components:

  • a user-interface script (ui.R) which controls the layout and appearance of your app
  • a server script (server.R) which contains the instructions needed to build the app You can actually run the app locally in RStudio by copying the following 2 R scripts
library(dplyr)
library(ggvis)
library(shiny)

shinyUI(fluidPage(
  
  h3("College Admissions"),
  p("Explore the distribution of SAT scores in different colleges"),

  sidebarLayout(position=c("right"),
    sidebarPanel(width=2,
      selectInput(inputId = "n_year", 
                  label = "Academic Year",
                  choices = c("(All)", "2013", "2014"),
                  selected = "(All)"),
      
      selectInput(inputId = "n_college", 
                  label = "College",
                  choices = c("(All)", "Arts & Sciences", "Business", "Communication", "Education", "Engineering", "Music", "Public Affairs", "Public Health"),
                  selected = "(All)"),
      
      selectInput(inputId = "n_gender",
                  label = "Gender",
                  choices = c("(All)", "Men", "Women"),
                  selected = "(All)")
      ),
    mainPanel(
      uiOutput("plot"), 
      ggvisOutput("ggvis")
    )
  )
))

library(dplyr)
library(ggvis)
library(shiny)

sat_score = read.csv("/Data/TableauDataSet_Education.csv")
sat_score$Total.Score < - as.numeric(as.character(sub(",", "", sat_score$Total.Score)))
sat_score$Academic.Year <- as.numeric(as.character(sub(",", "", sat_score$Academic.Year)))

shinyServer(function(input, output) {
  data <- reactive ({
    if (input$n_college == "(All)" &#038;&#038; input$n_gender == "(All)"  &#038;&#038; input$n_year == "(All)"){
      by_college <- group_by (sat_score, College, Total.Score)
      college_score <- summarise(by_college , NumberOfStudents = n())
    }
    else if (input$n_college == "(All)" &#038;&#038; input$n_gender == "(All)" &#038;&#038; input$n_year != "(All)"){
      by_college <- group_by (sat_score, College, Academic.Year, Total.Score)
      college_score <- summarise(by_college , NumberOfStudents = n())
      college_score <- filter(college_score, Academic.Year == input$n_year)
    }
    else if (input$n_college == "(All)" &#038;&#038; input$n_gender != "(All)" &#038;&#038; input$n_year != "(All)"){
      by_college <- group_by (sat_score, College, Gender, Academic.Year, Total.Score)
      college_score <- summarise(by_college , NumberOfStudents = n())
      college_score <- filter(college_score, Gender == input$n_gender, Academic.Year == input$n_year)
    }
    else if (input$n_college != "(All)" &#038;&#038; input$n_gender != "(All)" &#038;&#038; input$n_year != "(All)"){
      by_college <- group_by (sat_score, College, Gender, Academic.Year, Total.Score)
      college_score <- summarise(by_college , NumberOfStudents = n())
      college_score <- filter(college_score, College == input$n_college, Gender == input$n_gender, Academic.Year == input$n_year)
    }
    else if (input$n_college != "(All)" &#038;&#038; input$n_gender != "(All)" &#038;&#038; input$n_year == "(All)"){
      by_college <- group_by (sat_score, College, Gender, Total.Score)
      college_score <- summarise(by_college , NumberOfStudents = n())
      college_score <- filter(college_score, College == input$n_college, Gender == input$n_gender)
    }
    else if (input$n_college != "(All)" &#038;&#038; input$n_gender == "(All)" &#038;&#038; input$n_year == "(All)"){
      by_college <- group_by (sat_score, College, Total.Score)
      college_score <- summarise(by_college , NumberOfStudents = n())
      college_score <- filter(college_score, College == input$n_college)
    }
    else if (input$n_college != "(All)" &#038;&#038; input$n_gender == "(All)" &#038;&#038; input$n_year != "(All)"){
      by_college <- group_by (sat_score, College, Academic.Year, Total.Score)
      college_score <- summarise(by_college , NumberOfStudents = n())
      college_score <- filter(college_score, College == input$n_college, Academic.Year == input$n_year)
    }
    else if (input$n_college == "(All)" &#038;&#038; input$n_gender != "(All)" &#038;&#038; input$n_year == "(All)"){
      by_college <- group_by (sat_score, College, Gender, Total.Score)
      college_score <- summarise(by_college , NumberOfStudents = n())
      college_score <- filter(college_score, Gender == input$n_gender)
    }
  })
  
  college_tooltip <- function(x){
    with(sat_score[x$id, ], paste("<b>", "College of ", x$College, "<br />",
                                      "Total Score: ", "<b>", x$Total.Score, "</b><br />",
                                      "# number of Students: ", "<b>", x$NumberOfStudents, "</b><br />"))
  }

  data %>%
    ggvis(y=~NumberOfStudents, x=~Total.Score, stroke:="black", fill=~College) %>%
    layer_points() %>%
    add_axis("x", title="SAT Score") %>%
    add_axis("y", title="Number of Students") %>%
    add_tooltip(college_tooltip, "hover") %>%
    set_options(width=975, height=700) %>%
    bind_shiny("ggvis", "plot")
  data
})

I have published this app on Shiny for you to explore and interact with https://sfrechette.shinyapps.io/college_admissions

shinyapps.io-college_admissions

So from Tableau to R and Shiny we have almost the same data visualization and interactivity
I am using the ggvis package and it seems impossible to add a horizontal line to a plot for the average score… feature apparently not available yet!

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