datasetPrep.R

## This script stores some functions used for cleaning and homogeneizing the datasets

# clean function removes the betting attributes, removes Time attribute (not useful) and
# homogeneizes the date format in order to have the same date format in all datasets.
# It receives the dataframe.
# It returns the cleaned dataframe.

prepDataset <- function(df) {
  # Removing betting attributes from dataset
  df <- df[, - c(which(colnames(df) == "B365H"):ncol(df))]
  
  # Removing Time attribute in case it exists
  if (is.null(df$Time) == FALSE){
     df <- df[, - which(colnames(df) == "Time")]
  }

  # Homogeneizing Date attribute: dd/mm/yy

  date <- as.Date(df$Date, format = "%d/%m/%Y")
  date.df <- data.frame("dd" = as.numeric(format(date, format = "%d")),
                        "mm" = as.numeric(format(date, format = "%m")),
                        "yy" = as.numeric(format(date, format = "%y")))

  df <- data.frame(date.df, df[, c(3:23)])
  
  # Defining F/S Attibute (Fall or Spring):
  
  s.f <- rep("Spring", times=length(df$mm))
  s.f[which(df$mm >= 8 & df$mm <= 12)] <- "Fall"
  df <- data.frame("SF"=s.f, df)
  

  # Defining Season Attribute:
  
  if(df$yy[1]==15){
    df <- data.frame("Season"=rep("15/16", times = length(df$yy)), df)
  }
  if(df$yy[1]==16){
    df <- data.frame("Season"=rep("16/17", times = length(df$yy)), df)
  }
  if(df$yy[1]==17){
    df <- data.frame("Season"=rep("17/18", times = length(df$yy)), df)
  }
  if(df$yy[1]==18){
    df <- data.frame("Season"=rep("18/19", times = length(df$yy)), df)
  }
  if(df$yy[1]==19){
    df <- data.frame("Season"=rep("19/20", times = length(df$yy)), df)
  }
  
  return(df)
}


# wld function classifies the football game in win, loss or draw for a given team.
# It adds a column called WLD with class values: win, loss, draw (factor).
# It recieves two values: a season dataframe and the name of a team.
# It returns a dataframe containing football games for the given team and the new attibute WLD.

wld <- function(df, team) {
  
  df.team <- df[which(df$HomeTeam == team | df$AwayTeam == team), ]
  team.home <- which(df.team$HomeTeam == team)
  team.away <- which(df.team$AwayTeam == team)
  team.wld <- c()
  
  for (i in team.home) {
    if(df.team[i,]$FTHG > df.team[i,]$FTAG){
      team.wld[i] <- "win"
    }
    if(df.team[i,]$FTHG == df.team[i,]$FTAG){
      team.wld[i] <- "draw"
    }
    if(df.team[i,]$FTHG < df.team[i,]$FTAG){
      team.wld[i] <- "loss"
    }
  }
  
  for (i in team.away) {
    if(df.team[i,]$FTHG > df.team[i,]$FTAG){
      team.wld[i] <- "loss"
    }
    if(df.team[i,]$FTHG == df.team[i,]$FTAG){
      team.wld[i] <- "draw"
    }
    if(df.team[i,]$FTHG < df.team[i,]$FTAG){
      team.wld[i] <- "win"
    }
  }
  
  df.wld <- data.frame("WLD" = team.wld)
  df.team <- data.frame(df.team, df.wld)
  
  return(df.team)
}

# selectPred function selects predictors that can be known previously to the game
# It receives a dataframe and the target response
# It returns a new dataframe that contains the columns which would be used to predict 
# plus target response

selectPred <- function(df, targ){
  pred.cols <- c("Season", "SF", "HomeTeam", "AwayTeam", "Referee", targ)
  return(df[,pred.cols])
}

# homeTeam function selects rows in a dataframe for a given home team
# It receives a dataframe and the team name as a string
# It returns a new dataframe that contains rows with the given home team

homeTeam <- function(df, home.team){
  df <- df[c(which(df$HomeTeam == home.team)), ]
  return(df)
}

# awayTeam function selects rows in a dataframe for a given away team
# It receives a dataframe and the team name as a string
# It returns a new dataframe that contains rows with the given away team

awayTeam <- function(df, away.team){
  df <- df[c(which(df$AwayTeam == away.team)), ]
  return(df)
}


team <- function(df, team.name){
  df <- df[c(which(df$AwayTeam == team.name | df$HomeTeam == team.name)), ]
  return(df)
}