server.R

#
# This is the server logic of a Shiny web application. You can run the
# application by clicking 'Run App' above.
#
# Find out more about building applications with Shiny here:
#
#    http://shiny.rstudio.com/
#

# This is a shiny app to determine diamond price based on carat, cut, color, and clarity

library(shiny)
library(ggplot2)
library(curl)

# Define server logic
shinyServer(function(input, output) {
    
    # load data
    data("diamonds")
    
    # create the initial output
    output$distPlot <- renderPlot({
        
        # subset the data based on the inputs
        diamonds_sub <- subset(diamonds, cut == input$cut &
                                   color == input$color &
                                   clarity == input$clarity)
        
        # plot the diamond data with carat and price
        p <- ggplot(data = diamonds_sub, aes(x = carat, y = price)) + geom_point()
        p <- p + geom_smooth(method = "lm") + xlab("Carat") + ylab("Price")
        p <- p + xlim(0, 6) + ylim (0, 20000)
        p
    }, height = 700)
    
    # create linear model
    output$predict <- renderPrint({
        diamonds_sub <- subset( diamonds, cut == input$cut &
                                    color == input$color &
                                    clarity == input$clarity)
        fit <- lm(price~carat,data=diamonds_sub)
        unname(predict(fit, data.frame(carat = input$lm)))})
    
    observeEvent(input$predict, {distPlot <<- NULL
    output$distPlot <- renderPlot({p <- ggplot(data = diamonds, aes(x = carat, y = price)) + geom_point()
    p <- p + geom_smooth(method = "lm") + xlab("Carat") + ylab("Price")
    p <- p + xlim(0, 6) + ylim (0, 20000)
    p
    }, height = 700)})})