Shiny application to plot a baseball hitter's career trajectory

server.R

# setup work
library(Lahman)
library(dplyr) 

# create new data frame Batting.new by
# collapsing over stint variable
Batting.new <- summarise(group_by(Batting, playerID, yearID), 
                           AB = sum(AB),
                           H = sum(H),
                           X2B = sum(X2B),
                           X3B = sum(X3B),
                           HR = sum(HR),
                           SB = sum(SB),
                           BB = sum(BB),
                           SO = sum(SO),
                           HBP = sum(HBP),
                           SF = sum(SF),
                           SH = sum(SH))

# recode SF and SH values to 0
myrecode <- function(data, var){
  data[, var] <- ifelse(is.na(data[, var]), 0, data[, var])
  data
}
Batting.new <- myrecode(Batting.new, "SF")
Batting.new <- myrecode(Batting.new, "SH")

# define plate appearance variable
Batting.new$PA <- with(Batting.new, AB + BB + HBP + SF + SH)

# add age variable
Master$birthyear <- with(Master, 
                ifelse(birthMonth >= 7, birthYear + 1, birthYear))
Batting.new <- merge(Batting.new, 
      Master[, c("playerID", "nameFirst", "nameLast", "birthyear")],
      by="playerID")
Batting.new$Age <- with(Batting.new, yearID - birthyear)

# add first and last years variables
C.Years <- summarise(group_by(Batting, playerID), 
                     fYear=min(yearID),
                     lYear=max(yearID))
Batting.new <- merge(Batting.new, C.Years, by="playerID")

# Define server logic required to plot various variables 
# against year
shinyServer(function(input, output) {
  
  # Compute the forumla text in a reactive function since it is 
  # shared by the output$caption and output$mpgPlot functions
  formulaText <- reactive({
    firstlast <- unlist(strsplit(input$playername," "))
    playerids <- unique(subset(Batting.new, 
                    nameFirst==firstlast[1] & 
                    nameLast==firstlast[2])$playerID)
    d <- subset(Batting.new, playerID==playerids[input$num])
    paste(input$variable,"/",input$denom, 
          "Trajectory of ", input$playername,
          d$fYear[1], "-", d$lYear[1])
  })
  
  output$caption <- renderText({
    formulaText()
  })
  
  output$mpgPlot <- renderPlot({
    require(ggplot2)
    firstlast <- unlist(strsplit(input$playername," "))
    playerids <- unique(subset(Batting.new, 
                      nameFirst==firstlast[1] & 
                      nameLast==firstlast[2])$playerID)
    d <- subset(Batting.new, playerID==playerids[input$num])
    d$Rate <- d[, input$variable] / d[, input$denom]
    print(ggplot(d, aes(Age, Rate)) + 
            geom_point(size=5, color="red") +
            geom_smooth(method="loess", size=3) +
            theme(axis.text = element_text(size = rel(2))) + 
            theme(axis.title = element_text(size = rel(2))) +
            theme(plot.title = element_text(size = rel(2))) 
          ) 
  }, width=600, height=500)
})

ui.R

library(shiny)

shinyUI(pageWithSidebar(
  
  # Application title
  headerPanel("Career Trajectories"),
  
  # Sidebar with controls to select the variable to plot against mpg
  # and to specify whether outliers should be included
  sidebarPanel(
    textInput("playername", "Player Name:", value = "Mickey Mantle"),
    numericInput("num", "Number:", 1),
    selectInput("variable", "Variable:",
                list("Home Run Rate" = "HR",
                     "Batting Average" = "H", 
                     "Strikeout Rate" = "SO",
                     "Doubles Rate" = "X2B",
                     "Triples Rate" = "X3B",
                     "Walk Rate" = "BB",
                     "Hit By Pitch Rate" = "HBP"
                     )),
    selectInput("denom", "Denominator:",
                list("At Bats" = "AB",
                     "Plate Appearances" = "PA"
                ))
  ),
  
  # Show the caption and plot of the requested variable against mpg
  mainPanel(
    h3(textOutput("caption")),
    
    plotOutput("mpgPlot")
  )
))