Python and SQL with matplotlib.

# Quick hack to graph last 500 greenhouse temperatures from weather database.
import mariadb
import matplotlib.pyplot as plt
conn = mariadb.connect(user="pi",password="password",host="localhost",database="weather")
cur = conn.cursor()
tempIN     = []
tempOUT    = []
timestamps = []
# Get the most recent 500 records.
cur.execute("SELECT greenhouse_temperature, ambient_temperature, created FROM WEATHER_MEASUREMENT 
             ORDER BY created DESC LIMIT 500")
for i in cur:
    tempIN.append(i[0])
    tempOUT.append(i[1])
    timestamps.append(i[2])  
conn.close()
plt.figure(figsize=(14, 6))
plt.title(label="Greenhouse and outside temperature up to "+str(timestamps[0]))
plt.xlabel("Date and time")
plt.ylabel("Temperature in Celsius")
plt.plot(timestamps, tempIN, label='Greenhouse temperature')
plt.plot(timestamps, tempOUT, label='Outside temperature')
plt.axhline(y=5.0, color='r', linestyle='-.')
plt.legend()
plt.savefig("/var/www/html/GHtemp.jpg")
plt.show()
Me, wearing a Panama hat, spectacles, and a fine growth of facial hair.

Author: Walrus

Just this guy, you know. To be continued...