import csv
import matplotlib.pyplot as plt
import sys
from datetime import datetime

# Usage: python plot_col2.py [csvfile]
csvfile = sys.argv[1] if len(sys.argv) > 1 else 'humidistat_data.csv'
dates = []
col2 = []

with open(csvfile, 'r') as f:
    reader = csv.reader(f)
    for row in reader:
        if len(row) > 1:
            try:
                # Parse date/time from field 1
                dt = datetime.strptime(row[0].replace('T', ' '), '%Y-%m-%d %H:%M:%S')
                val = float(row[1])
                dates.append(dt)
                col2.append(val)
            except Exception:
                continue

plt.figure(figsize=(10,4))
plt.plot(dates, col2, marker='o', linestyle='-')
plt.title('Column 2 vs Date')
plt.xlabel('Date/Time')
plt.ylabel('Value')
plt.grid(True)
plt.tight_layout()
plt.gcf().autofmt_xdate()
plt.show()