Calculate x intercept for Pennsylvania ballot counting

calculate_margin_intercept.py

#!/usr/bin/env python3

# Calculates expected time that Biden will overtake Trump in Pennsylvania
# base on time series data: margin over time.
#
# Example usage:
# $ curl "https://raw.githubusercontent.com/alex/nyt-2020-election-scraper/master/battleground-state-changes.csv" | ./calculate_margin_intercept.py 

import csv
import datetime
import sys
import numpy as np

def _YieldRecords():
  reader = csv.DictReader(sys.stdin)
  yield from reader
    
def _FilteredRecords():
  for record in _YieldRecords():
    if 'Pennsylvania' in record['state']:
      yield record

def _YieldDataPoints():
  # Ignore times before noon wed
  cutoff = datetime.datetime.fromisoformat(    
    '2020-11-05 12:00:00-05:00')
  
  for record in _FilteredRecords():
    margin = int(record['vote_differential'])

    # source data is UTC
    timestamp = datetime.datetime.fromisoformat(
      record['timestamp']).replace(tzinfo=datetime.timezone.utc)

    if timestamp >= cutoff:
      unix_timestamp = datetime.datetime.timestamp(timestamp) 
      yield unix_timestamp, margin
    
def main():
  points = list(_YieldDataPoints())
  x = [d[0] for d in points]
  y = [d[1] for d in points]

  model = np.polyfit(x, y, 1)
  a , b = model

  # y = a * x + b
  # y - b = a * x
  # 0 - b = a * x
  # x = (0 - b) / a
  intersection = b / -a

  print('Intersection timestamp:', intersection)

main()