From b7b5b6e0c1309d9c8bf0510c878a63aa0b80c885 Mon Sep 17 00:00:00 2001
From: Florian Pritz <bluewind@xinu.at>
Date: Tue, 20 Jun 2017 15:15:15 +0200
Subject: Plot absolute humidity

Signed-off-by: Florian Pritz <bluewind@xinu.at>
---
 plot.py | 31 ++++++++++++++++++++++---------
 1 file changed, 22 insertions(+), 9 deletions(-)

diff --git a/plot.py b/plot.py
index 535398e..647a083 100755
--- a/plot.py
+++ b/plot.py
@@ -13,6 +13,7 @@
 import sys
 import subprocess
 import os
+import math
 from string import Template
 
 if len(sys.argv) != 3:
@@ -28,7 +29,7 @@ argmax = 50000
 
 # If you change this you also need to change the create and graph lists below.
 # Also note that samples have to be in the same order every time (the key is currently ignored).
-samples_per_line=3
+samples_per_line=2
 
 template_values = {
 	# 0 = everything from the input
@@ -45,7 +46,8 @@ create = [
 
 	'DS:temp1:GAUGE:50:U:U',
 	'DS:temp2:GAUGE:50:U:U',
-	'DS:hum1:GAUGE:50:U:U',
+	#'DS:hum1:GAUGE:50:U:U',
+	'DS:abshum1:GAUGE:50:U:U',
 
 	'RRA:AVERAGE:0.5:1:$total_samples',
 	'RRA:MIN:0.5:1:$total_samples',
@@ -61,10 +63,10 @@ graph = [
 	'--color=BACK#FFFFFF',
 	#'--title','Temperature',
 	'--vertical-label', 'Temperature °C',
-	'--right-axis-label', 'Humidity %',
-	'--right-axis', '2:0',
-	'--alt-autoscale',
-	#'-l','25','-u','30',
+	'--right-axis-label', 'Humidity g/m³',
+	'--right-axis', '0.5:0',
+	#'--alt-autoscale',
+	'-l','10','-u','35', '--rigid',
 	'--left-axis-format', '%4.2lf',
 	'--right-axis-format', '%4.2lf',
 
@@ -72,9 +74,12 @@ graph = [
 	'LINE1:temp1#339966:temp 1\l',
 	'DEF:temp2='+rrd_file+':temp2:AVERAGE',
 	'LINE1:temp2#663399:temp 2\l',
-	'DEF:hum1='+rrd_file+':hum1:AVERAGE',
-	'CDEF:hum11=hum1,2,/',
-	'LINE1:hum11#996633:hum 1\l',
+	#'DEF:hum1='+rrd_file+':hum1:AVERAGE',
+	#'CDEF:hum11=hum1,2,/',
+	#'LINE1:hum11#996633:hum 1\l',
+	'DEF:abshum1='+rrd_file+':abshum1:AVERAGE',
+	'CDEF:abshum11=abshum1,2,*',
+	'LINE1:abshum11#996633:abshum 1\l',
 ]
 
 #### end of config
@@ -100,6 +105,14 @@ with open(log_file,"r") as f:
 		# values
 		for i in range(1, samples_per_line + 1):
 			values.append(float(elem[i].split("=")[1]))
+
+		# absolute humidity
+		hum=float(elem[3].split("=")[1])
+		temp=values[2]
+		# Source: https://carnotcycle.wordpress.com/2012/08/04/how-to-convert-relative-humidity-to-absolute-humidity/
+		abshum=(6.112 * math.e**(17.67 * temp / (temp + 243.5)) * hum * 2.1674) / (273.15+temp)
+		values.append(abshum)
+
 		samples.append(values)
 
 # create rrd
-- 
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