R function to plot home run rate, strikeout rate, walk rate, and wOBA for a specific baseball hitter.

plot_rates.R

plot_rates <- function(player_name){
  require(Lahman)
  require(tidyverse)
  require(gridExtra)
  require(baseballr)
  wts <- fg_guts()

  names <- unlist(str_split(player_name, " "))
  Master %>% filter(nameLast == names[2],
                  nameFirst == names[1]) %>% 
  select(playerID) -> d

  Batting %>% filter(playerID == d$playerID) %>%
  group_by(yearID) %>%
  summarize(AB = sum(AB),
            BIP = sum(AB) - sum(SO),
            H = sum(H),
            HR = sum(HR),
            SO = sum(SO),
            BB = sum(BB),
            IBB = sum(IBB),
            X2B = sum(X2B),
            X3B = sum(X3B),
            HBP = sum(HBP),
            SF = sum(SF)) %>%
  mutate(X1B = H - X2B - X3B - HR,
         uBB = BB - IBB,
         Year = as.character(yearID)) -> pdata

  inner_join(pdata, wts, by=c("yearID" = "season")) ->
  pdata

  pdata %>% mutate(wOBA = (wBB * uBB + wHBP * HBP +
         w1B * X1B + w2B * X2B + w3B * X3B + wHR * HR) /
        (AB + BB - IBB - SF + HBP)) -> pdata

  Batting %>% filter(yearID %in% pdata$yearID) %>%
  group_by(yearID, playerID) %>%
  summarize(AB = sum(AB),
            BIP = sum(AB) - sum(SO),
            H = sum(H),
            HR = sum(HR),
            SO = sum(SO),
            BB = sum(BB),
            IBB = sum(IBB),
            X2B = sum(X2B),
            X3B = sum(X3B),
            HBP = sum(HBP),
            SF = sum(SF)) %>% 
  filter(AB >= 300) %>%
  mutate(Year = as.character(yearID),
         X1B = H - X2B - X3B - HR,
         uBB = BB - IBB) -> S1

  inner_join(S1, wts, by=c("yearID" = "season")) ->
  S1

  S1 %>% mutate(wOBA = (wBB * uBB + wHBP * HBP +
w1B * X1B + w2B * X2B + w3B * X3B + wHR * HR) /
                   (AB + BB - IBB - SF + HBP)) -> S1

  TH <- theme(
  plot.title = element_text(
    colour = "blue",
    size = 16,
    hjust = 0.5,
    vjust = 0.8,
    angle = 0
  ))
  
  p1 <- ggplot(S1, aes(Year, HR / BIP)) +
  geom_boxplot() +
  geom_point(data = pdata,
            aes(Year, HR / (AB - SO), 
                group=player_name),
            color="red", size=2.5) +
  ggtitle("Home Run Rate") + TH + xlab("") +
  theme(axis.text.x = element_text(angle = 60, 
                                   hjust = 1))

  p2 <- ggplot(S1, aes(Year, SO / (AB + BB))) +
  geom_boxplot() +
  geom_point(data = pdata,
             aes(Year, SO / (AB + BB),
                group=player_name),
             color="red", size=2.5) +
  ggtitle("Strikeout Rate") + TH + xlab("") +
  theme(axis.text.x = element_text(angle = 60, 
                                   hjust = 1))

  p3 <- ggplot(S1, aes(Year, BB / (AB + BB))) +
  geom_boxplot() +
  geom_point(data = pdata,
             aes(Year, BB / (AB + BB),
              group=player_name),
             color="red", size=2.5) +
  ggtitle("Walk Rate") + TH + xlab("") +
  theme(axis.text.x = element_text(angle = 60, 
                                   hjust = 1))

  p4 <- ggplot(S1, aes(Year, wOBA)) +
  geom_boxplot() +
  geom_point(data = pdata,
             aes(Year, wOBA,
            group=player_name),
             color="red", size=2.5) +
  ggtitle("wOBA") + TH + xlab("") +
  theme(axis.text.x = element_text(angle = 60, 
                                   hjust = 1))

  grid.arrange(p1, p2, p3, p4, ncol=2,
             top=player_name)
}