Fantasy Football - How Optimal Have Your Transfer Decisions Been?

Track record for blogging experiments up to date - disastrous.

Let’s try this one more time.

I enjoy watching Soccer and have been playing Fantasy Football for a little time now. Premier League is one of the toughest leagues in the world with briliant football players who compete for the title. Great respect for the players and the coaches who handle the pressure and keep playing, every week of the year and then do it all over again. Fantasy Football itself is quite addictive, a super fun ride (though most certainly painful).

This ofcourse made me wonder if there is an “optimal” way to play the game and if algorithms can be designed around it. I think this ia particularly challenging problem even with the hoard of the data collected and statistics created around the players, team fixtures, different techniques used by the coaches. There are so many uncertain factors in the game, it comes down to trying to predict human behaviour and the uncertainty created by chance occurences. But without falling too deep into that wormhole, my experiment is much simpler. My objective was to see how optimal my transfer decisions had been from gameweek-to-gameweek. I wanted to see what my team would look like if I had the exact same team throughout as I did in the beginning of the season (GW 1) versus how it performed with my transfer decisions. Here is my Gameweek 1 team for this season:

FPL-GW1-Team

The code walkthrough for this experiment is below. I do use a randomly chosen league for demonstration purposes. The website has an API which makes it easy to analyze and collect the data. This script does require having the “FPL_EMAIL” and “FPL_PASSWORD” environment variables correctly populated.

import requests
import json
import numpy as np
import pandas as pd
import datetime
from pprint import pprint

import asyncio
import aiohttp
from fpl import FPL

async def my_team(user_id):
    async with aiohttp.ClientSession() as session:
        fpl = FPL(session)
        await fpl.login()
        # login is required for private(?) leagues
        user = await fpl.get_user(user_id)
        team = await user.get_team()
        h2h_league = await fpl.get_classic_league(2)
        league_players = dict(( player['player_name'], player['entry']) for player in h2h_league.standings['results'][10:30])
        return league_players

league_players = await my_team(5827336)
# final gameweek to be considered.
gameweek_last = 7

Next, we have a function to determine the total points gained by a particular player in their gameweek history.

def get_player_total_points(element, is_captain, multiplier):
    '''
    Retrieve total points of a football player until `gameweek_last` GW.
    
    The starting 11 players from the 1st Gameweek's team are used to 
    calculate total points for the static team until `gameweek_last`.
    If players on the bench would have substituted one of the 11 players,
    this scenario is excluded from the calculation thereby only providing
    an approximation.
    
    The player that was captained in the 1st GW gets double the points.
    The scenario where the captain is substituted by the vice captain
    is also excluded from the calculation.
    '''
    link = "https://fantasy.premierleague.com/api/element-summary/{}/".format(element)
    response = requests.get(link)
    data = json.loads(response.text)

    # get total points of player
    tp = 0
    tp_by_gw = []
    for k in data['history']:
        if k['round']>gameweek_last:
            continue
        if 'total_points' in k:
            if is_captain:
                tp+= k['total_points']*2
            else:
                tp+= k['total_points']*multiplier
            tp_by_gw.append(tp)    
    
    return tp, tp_by_gw

Finally, we get all the information together for the manager’s total points with managed teams and total points with static teams.

players = {}
for player, player_id in league_players.items():
    link = 'https://fantasy.premierleague.com/api/entry/{}/'.format(player_id)
    response = requests.get(link)
    data = json.loads(response.text)
    summary_overall_points = data['summary_overall_points']
    
    # get total points of manager's team in gameweek history
    gw_points = []
    for gw in range(1,gameweek_last):
        link = 'https://fantasy.premierleague.com/api/entry/{}/event/{}/picks/'.format(player_id,gw)
        response = requests.get(link)
        data = json.loads(response.text)
        gw_points.append(data['entry_history']['total_points'])
    
    link = 'https://fantasy.premierleague.com/api/entry/{}/event/1/picks/'.format(player_id)
    response = requests.get(link)
    data = json.loads(response.text)
    total_points = 0
    players_points = {}
    gw_points_if_first_team = []
    
    # cycle through each player picked by manager
    # get total points in gameweek history
    for entry in data['picks']:
        element = entry['element']
        if entry['multiplier']:
            element_tp, tp_points_by_gw = get_player_total_points(element, entry['is_captain'], entry['multiplier'])
            players_points[player_names[int(element)]] = element_tp
            gw_points_if_first_team.append(np.array(tp_points_by_gw))
    
    gw_points_if_first_team = np.sum(np.array(gw_points_if_first_team),axis=0)
    
    total_points = sum([v for k,v in players_points.items()])
    players[player] = {'team':players_points,'total_points':total_points,
                       'summary_overall_points':summary_overall_points,
                       'gw_points':gw_points,
                       'gw_points_if_first_team':gw_points_if_first_team
                      }
    print(player,players[player])

Enough with the code, I plotted the cumulative sum of the gameweek total points based on both scenarios to get this graph:

Total Points Cumsum

And a summary with the percentage gains of actively making transfer decision over having the static team:

Transfer Gain Summary

My personal stats for last season were actually decently sad with only a 7% gain when actively managing the team. Some of my teammates in the league fared far worse though with a negative gain. Goes to show, sometimes in life, it’s better to be a couch potato!

Homercat