• Does enhancing car features reduce its mileage?
• We will answer the above question by regressing certain car features with miles per gallon using 'mtcars' dataset.
• The results are highlighted in the form of a scatterplot involving a fitted line.
• The user can also opt to see the slope coefficient and a conclusion based on the results.
• Snippet of ui.R and server.R is presented in the slides. The R codes are available on Github.
• The interactive panel and output is available at: Shinyapps.io

str(mtcars)

'data.frame':   32 obs. of  11 variables:
 $ mpg : num  21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ...
 $ cyl : num  6 6 4 6 8 6 8 4 4 6 ...
 $ disp: num  160 160 108 258 360 ...
 $ hp  : num  110 110 93 110 175 105 245 62 95 123 ...
 $ drat: num  3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ...
 $ wt  : num  2.62 2.88 2.32 3.21 3.44 ...
 $ qsec: num  16.5 17 18.6 19.4 17 ...
 $ vs  : num  0 0 1 1 0 1 0 1 1 1 ...
 $ am  : num  1 1 1 0 0 0 0 0 0 0 ...
 $ gear: num  4 4 4 3 3 3 3 4 4 4 ...
 $ carb: num  4 4 1 1 2 1 4 2 2 4 ...

library(shiny)
library(dplyr)
options(digits=2)
cars <- select(mtcars, cyl, hp, wt, disp, drat)
shinyUI(fluidPage(
    titlePanel('Miles per Gallon and Car Features'),
    sidebarLayout(
        sidebarPanel(
            selectInput('yin', 'Choose a feature (dependent variable)', names(cars),
                        selected=names(cars)[[1]]),
            h1(""),
            checkboxInput("showFit1", "Show Fitted Line", value = TRUE),
            checkboxInput("showbeta1", "Show Slope Coefficient", value = TRUE),
            checkboxInput("showConclusion", "Show Statement", value = TRUE),
            h5("First 8 Observations"), 
            tableOutput('table')),
        mainPanel(


            h3("Question: Does enhancing features of cars reduce its miles per gallon?"),
            h6("Note: Data extracted from 'mtcars' dataset"),
            h3("Answer:"),
            plotOutput("plot1"),
            h4("Slope Coefficient and conclusion is:"),
            textOutput("beta1"),
            textOutput("beta2"),
            textOutput("beta3"),
            textOutput("beta4"),
            textOutput("beta5"),

            textOutput("text1"),
            textOutput("text2"),
            textOutput("text3"),
            textOutput("text4"),
            textOutput("text5")
        )
    )
))

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library(ggplot2)
library(shiny)
mtcars2<-mtcars
shinyServer(function(input, output) {
    selectedData <- reactive({
        mtcars[, c("mpg", input$yin)]})

    lm1 <- lm(cyl ~ mpg, data = mtcars)
    lm2 <- lm(wt ~ mpg, data = mtcars)
    lm3 <- lm(hp ~ mpg, data = mtcars)
    lm4 <- lm(disp ~ mpg, data = mtcars)
    lm5 <- lm(drat ~ mpg, data = mtcars)

    output$plot1 <- renderPlot({
        par(mar = c(5.1, 4.1, 0, 1))
        plot(selectedData(),
         pch=20, cex = 3, xlab = "Miles per Gallon", ylab = input$yin)
        if(input$showFit1){  
        if(input$yin=='cyl'){abline(lm1, col = "red", lwd = 2)}
        if(input$yin=='wt'){abline(lm2, col = "green", lwd = 2)}
        if(input$yin=='hp'){abline(lm3, col = "blue", lwd = 2)}
        if(input$yin=='disp'){abline(lm4, col = "orange", lwd = 2)}
        if(input$yin=='drat'){abline(lm5, col = "purple", lwd = 2)}    
        }

    })



    output$beta1 <- renderText({if(input$yin=='cyl' & input$showbeta1){lm1[[1]][2]}})
    output$beta2 <- renderText({if(input$yin=='wt' & input$showbeta1 ){lm2[[1]][2]}})
    output$beta3 <- renderText({if(input$yin=='hp' & input$showbeta1 ){lm3[[1]][2]}})
    output$beta4 <- renderText({if(input$yin=='disp' & input$showbeta1 ){lm4[[1]][2]}})
    output$beta5 <- renderText({if(input$yin=='drat' & input$showbeta1 ){lm5[[1]][2]}})

    output$text1 <- renderText({if(input$yin=='cyl' & input$showConclusion){"Greater the number of cylinders lower the MPG"}})
    output$text2 <- renderText({if(input$yin=='wt' & input$showConclusion){"Greater the weight lower the MPG"}})
    output$text3 <- renderText({if(input$yin=='hp' & input$showConclusion){"Greater the horsepower lower the MPG"}})
    output$text4 <- renderText({if(input$yin=='disp' & input$showConclusion){"Greater the displacement lower the MPG"}})
    output$text5 <- renderText({if(input$yin=='drat' & input$showConclusion){"Larger the drat (real axle ratio)  higher the MPG"}})

    output$table <- renderTable({
        head(selectedData(),8)})
})