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MLB runs per game (Lahman database)

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# load the package and data set "Teams"

install.packages("Lahman")

library("Lahman")

data(Teams)

#

#

# CREATE LEAGUE SUMMARY TABLES

# ============================

#

# select a sub-set of teams from 1901 [the establishment of the American League] forward to 2012

Teams_sub <- as.data.frame(subset (Teams, yearID > 1900))

#

# calculate each team's average runs and runs allowed per game

Teams_sub$RPG <- Teams_sub$R / Teams_sub$G          

Teams_sub$RAPG <- Teams_sub$RA / Teams_sub$G					

#

# create new data frame with season totals for each league

LG_RPG <- aggregate(cbind(R, RA, G) ~ yearID + lgID, data = Teams_sub, sum)

# calculate league + season runs and runs allowed per game

LG_RPG$LG_RPG <- LG_RPG$R / LG_RPG$G

LG_RPG$LG_RAPG <- LG_RPG$RA / LG_RPG$G

#

# select a sub-set of teams from 1901 [the establishment of the American League] forward to 2012

# read the data into separate league tables

ALseason <- (subset (LG_RPG, yearID > 1900 & lgID == "AL"))

NLseason <- (subset (LG_RPG, yearID > 1900 & lgID == "NL"))

#

# +++++++++++++++++++++++++++++++++++++++++++++++++++

#

# RUNS SCORED PER GAME

# ====================

#

# web references: 

#  http://princeofslides.blogspot.ca/2011/05/sab-r-metrics-basics-of-loess.html 

#  http://research.stowers-institute.org/efg/R/Statistics/loess.htm

#

# start with American League

# create new object ALRunScore.LO for loess model

ALRunScore.LO <- loess(ALseason$LG_RPG ~ ALseason$yearID)    		

ALRunScore.LO.predict <- predict(ALRunScore.LO)

#

# create new objects RunScore.Lo.XX for loess models with "span" control

ALRunScore.LO.25 <- loess(ALseason$LG_RPG ~ ALseason$yearID, span=0.25)				

ALRunScore.LO.25.predict <- predict(ALRunScore.LO.25)

#

ALRunScore.LO.5 <- loess(ALseason$LG_RPG ~ ALseason$yearID, span=0.5)				

ALRunScore.LO.5.predict <- predict(ALRunScore.LO.5)

#

# plot the data, add loess curve

ylim <- c(3,6)

plot(ALseason$LG_RPG ~ ALseason$yearID, 

     ylim = ylim, 

     main = "American League: runs per team per game, 1901-2012", 

     xlab = "year", ylab = "runs per game")

# loess predicted value line

lines(ALseason$yearID, ALRunScore.LO.predict, lty="solid", col="red", lwd=2)

lines(ALseason$yearID, ALRunScore.LO.25.predict, lty="dashed", col="blue", lwd=2)

lines(ALseason$yearID, ALRunScore.LO.5.predict, lty="dotdash", col="black", lwd=2)

legend(1980, 3.5, 

       c("default", "span=0.25", "span=0.50"), 

       lty=c("solid", "dashed", "dotdash"), 

       col=c("red", "blue", "black"), 

       lwd=c(2, 2, 2))

grid()

#

# NATIONAL LEAGUE

# create new object RunScore.LO for loess model

NLRunScore.LO <- loess(NLseason$LG_RPG ~ NLseason$yearID)				

NLRunScore.LO.predict <- predict(NLRunScore.LO)

#

# objects with span control in loess model

NLRunScore.LO.25 <- loess(NLseason$LG_RPG ~ NLseason$yearID, span=0.25)				

NLRunScore.LO.25.predict <- predict(NLRunScore.LO.25)

NLRunScore.LO.5 <- loess(NLseason$LG_RPG ~ NLseason$yearID, span=0.5)				

NLRunScore.LO.5.predict <- predict(NLRunScore.LO.5)

#

# plot the data, add loess curve

ylim <- c(3,6)

plot(NLseason$LG_RPG ~ NLseason$yearID, 

     pch=2, col="black",

     ylim = ylim, 

     main = "National League: runs per team per game, 1901-2012", 

     xlab = "year", ylab = "runs per game")

# loess predicted value line

lines(NLseason$yearID, NLRunScore.LO.predict, lty="solid", col="blue", lwd=2)

lines(NLseason$yearID, NLRunScore.LO.25.predict, lty="dashed", col="red", lwd=2)

lines(NLseason$yearID, NLRunScore.LO.5.predict, lty="dotdash", col="black", lwd=2)

# chart tidying

legend(1980, 3.5, 

       c("default", "span=0.25", "span=0.50"), 

       lty=c("solid", "dashed", "dotdash"), 

       col=c("blue", "red", "black"), 

       lwd=c(2, 2, 2))

grid()

#

#

# MULTI-PLOT -- MERGING AL AND NL RESULTS

# plot individual years as lines

ylim <- c(3,6)

# start with AL line

plot(ALseason$LG_RPG ~ ALseason$yearID,

     type="l", lty="solid", col="red", lwd=2,

     main = "Runs per team per game, 1901-2012", 

     ylim = ylim, 

     xlab = "year", ylab = "runs per game")

# add NL line

lines(NLseason$yearID, NLseason$LG_RPG, lty="solid", col="blue", lwd=2)

# chart additions

grid()

legend(1900, 3.5, c("AL", "NL"), lty=c("solid", "solid"), col=c("red", "blue"), lwd=c(2, 2))

#

#

# plot loess curves (span=0.25)

ylim <- c(3,6)

# start with AL line

plot(ALRunScore.LO.25.predict ~ ALseason$yearID,

     type="l", lty="solid", col="red", lwd=2,

     main = "Runs per team per game, 1901-2012", 

     ylim = ylim, 

     xlab = "year", ylab = "runs per game")

# add NL line

lines(NLseason$yearID, NLRunScore.LO.25.predict, lty="dashed", col="blue", lwd=2)

# chart additions

legend(1900, 3.5, 

       c("AL (span=0.25)", "NL (span=0.25)"), 

       lty=c("solid", "dashed"), 

       col=c("red", "blue"), 

       lwd=c(2, 2))

grid()

#

#

# plot loess curves (span=0.50)

ylim <- c(3,6)

# start with AL line

plot(ALRunScore.LO.5.predict ~ ALseason$yearID,

     type="l", lty="solid", col="red", lwd=2,

     main = "Runs per team per game, 1901-2012", 

     ylim = ylim, 

     xlab = "year", ylab = "runs per game")

# add NL line

lines(NLseason$yearID, NLRunScore.LO.5.predict, lty="dashed", col="blue", lwd=2)

# chart additions

legend(1900, 3.5, 

       c("AL (span=0.50)", "NL (span=0.50)"), 

       lty=c("solid", "dashed"), 

       col=c("red", "blue"), 

       lwd=c(2, 2))

grid()

#

#

#

# plot multiple loess curves (span=0.50 and 0.25)

ylim <- c(3,6)

# start with AL line

plot(ALRunScore.LO.5.predict ~ ALseason$yearID,

     type="l", lty="solid", col="red", lwd=2,

     main = "Runs per team per game, 1901-2012", 

     ylim = ylim, 

     xlab = "year", ylab = "runs per game")

# add NL line

lines(NLseason$yearID, NLRunScore.LO.5.predict, lty="solid", col="blue", lwd=2)

# add 0.25 lines

lines(ALseason$yearID, ALRunScore.LO.25.predict, lty="dashed", col="red", lwd=2)

lines(NLseason$yearID, NLRunScore.LO.25.predict, lty="dashed", col="blue", lwd=2)

# chart additions

legend(1900, 3.5, 

       c("AL (span=0.50)", "NL (span=0.50)", "AL (span=0.25)", "NL (span=0.25)"), 

       lty=c("solid", "solid", "dashed", "dashed"), 

       col=c("red", "blue", "red", "blue"), 

       lwd=c(2, 2, 2, 2))

grid()

#

# # # # # # # # # # # # # # # # # #

#

# calculate the difference between the two leagues 

# 1. absolute

RunDiff <- (ALseason$LG_RPG - NLseason$LG_RPG)

# 2. LOESS span=0.25

RunDiffLO <- (ALRunScore.LO.25.predict - NLRunScore.LO.25.predict)

#

# plot the LOESS difference

ylim <- c(-1,1)

plot(RunDiffLO ~ ALseason$yearID,

     type="l", lty="solid", col="red", lwd=2,

     main = "Run scoring trend: AL difference from NL, 1901-2012", 

     ylim = ylim, 

     xlab = "year", ylab = "runs per game")

# add line at zero

abline(h = 0, lty="dotdash") 

grid()

#

# plot each year difference as line, trend as line

ylim <- c(-1,1.5)

plot(RunDiffLO ~ ALseason$yearID,

     type="l", lty="solid", col="red", lwd=3,

     main = "Run scoring trend: AL difference from NL, 1901-2012", 

     ylim = ylim, 

     xlab = "year", ylab = "runs per game")

# add RunDiff line

lines(ALseason$yearID, RunDiff, lty="solid", col="black", lwd=1)

# add line at zero

abline(h = 0, lty="dotdash") 

grid()

#

#

# plot each year difference as bar, trend as line

ylim <- c(-1,1.5)

plot(RunDiff ~ ALseason$yearID,

     type="h", lty="solid", col="blue", lwd=2,

     main = "Run scoring trend: AL difference from NL, 1901-2012", 

     ylim = ylim, 

     xlab = "year", ylab = "runs per game")

# add RunDiff line

lines(ALseason$yearID, RunDiffLO, lty="solid", col="black", lwd=2)

# add line at zero

abline(h = 0, lty="dotdash") 

# chart additions

grid()

legend(1900, 1.5, 

       c("AL difference from NL: absolute", "AL difference from NL, LOESS (span=0.25)"), 

       lty=c("solid", "solid"), 

       col=c("blue", "black"), 

       lwd=c(2, 2))

#

#
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