data(SeriesPost)

data(SeriesPost)

# How many times has each team won the World Series?

# Notes: 
# - the SeriesPost table includes an identifier for the 
# team (teamID), but not the franchise (e.g. the Brooklyn Dodgers
# [BRO] and Los Angeles Dodgers [LAN] are counted separately)
#
# - the World Series was first played in 1903, but the 
# Lahman data tables have the final round of the earlier 
# playoffs labelled "WS", so it is necessary to
# filter the SeriesPost table to exclude years prior to 1903. 

# using the dplyr data manipulation package
library("dplyr")
library("tidyr")
library("ggplot2")

## WS winners, arranged in descending order of titles won
ws_winner_table <- SeriesPost %>%
  filter(yearID > "1902", round == "WS") %>%
  group_by(teamIDwinner) %>%
  summarise(wincount = n()) %>%
  arrange(desc(wincount))
ws_winner_table

## Expanded form of World Series team data in modern era

ws <- SeriesPost %>%
        filter(yearID >= 1903 & round == "WS") %>%
        select(-ties, -round) %>%
        mutate(lgIDloser = droplevels(lgIDloser),
               lgIDwinner = droplevels(lgIDwinner))

# Bar chart of length of series (# games played)
# 1903, 1919 and 1921 had eight games
ggplot(ws, aes(x = wins + losses)) +
  geom_bar(fill = "dodgerblue") +
  labs(x = "Number of games", y = "Frequency")

# Last year the Cubs appeared in the WS
ws %>% 
  filter(teamIDwinner == "CHN" | teamIDloser == "CHN") %>% 
  summarise(max(yearID))

# Dot chart of number of WS appearances by teamID
ws %>% 
  gather(wl, team, teamIDwinner, teamIDloser) %>%
  count(team) %>%
  arrange(desc(n)) %>%
  ggplot(., aes(x = reorder(team, n), y = n)) +
    theme_bw() +
    geom_point(size = 3, color = "dodgerblue") +
    geom_segment(aes(xend = reorder(team, n), yend = 0), 
                 linetype = "dotted", color = "dodgerblue", 
                 size = 1) +
    labs(x = NULL, y = "Number of WS appearances") +
    scale_y_continuous(expand = c(0, 0), limits = c(0, 42)) +
    coord_flip() +
    theme(axis.text.y = element_text(size = rel(0.8)),
          axis.ticks.y = element_blank())

# Initial year of each round of championship series in modern era
SeriesPost %>% 
    filter(yearID >= 1903) %>%   # modern WS started in 1903
    group_by(round) %>%
    summarise(first_year = min(yearID)) %>%
    arrange(first_year)

# Ditto, but with more information about each series played
SeriesPost %>% 
  filter(yearID >= 1903) %>%
  group_by(round) %>%
  arrange(yearID) %>%
  do(head(., 1)) %>%
  select(-lgIDwinner, -lgIDloser) %>%
  arrange(yearID, round)