fix datetime in plot

diff --git a/plot_mhz19.py b/plot_mhz19.py
index fc3976ad005ef7b1b440d6a6557a3c57cbf04f9a..0e68605745d79cfe05f1251ae3f875bb5cc11132 100755 (executable)
--- a/plot_mhz19.py
+++ b/plot_mhz19.py
@@ -1,6 +1,7 @@
 #!/usr/bin/python3
 
 import csv
+from datetime import datetime, date, timedelta
 from matplotlib import pyplot as plt
 
 filename = 'log.csv'
@@ -10,20 +11,29 @@ Time,TS,CO2,Temp
 21:02:08,5021,657,24
 
 '''
+
+def parsedatetime(timevalue, currentdate):
+    dt = datetime.strptime(timevalue, '%H:%M:%S')
+    return datetime.combine(currentdate, dt.time())
+
 with open(filename) as f:
     reader = csv.reader(f)
     headers = next(reader)
 
     time = []
     co2 = []
+    startdate = date(2020, 10, 22)
     for row in reader:
-        time.append(row[0])
+        dt = parsedatetime(row[0], startdate)
+        if len(time) > 0 and dt - time[-1] < timedelta(hours=-2): # DST switch!
+            startdate += timedelta(days=1)
+            dt += timedelta(days=1)
+        time.append(dt)
         co2.append(int(row[2]))
 
-    fig = plt.figure(dpi = 128, figsize = (10,6))
-    plt.plot(co2, c = 'red')
-    plt.title('CO₂', fontsize = 24)
-    plt.xlabel('',fontsize = 16)
-    plt.ylabel('ppm', fontsize = 16)
-    plt.tick_params(axis = 'both', which = 'major', labelsize = 16)
+    plt.plot(time, co2, c = 'red')
+    plt.title('CO₂')
+    plt.xlabel('time')
+    plt.ylabel('ppm')
+    plt.tick_params(axis = 'both', which = 'major')
     plt.show()