Why not do it in two steps? First, make a call to RRDs::fetch to obtain the min and max values of the value you want to graph over the time period in question. Second, use these values to calculate a round number to use as min/max. Third, use your preferred temperature min/max to calculate an appropriate scaleshift for the humidity; if the temp is from A to B, then set scaleshift for the second axis to (100/(B-A)):-A and have the second value display as (X/100*(B-A)+A)
This should achieve what you want. Of course, you cant do it from rrdcgi, but if you're generating the graph programmatically from the libraries it shouldnt be a problem. Steve Steve Shipway University of Auckland ITS UNIX Systems Design Lead [email protected] Ph: +64 9 373 7599 ext 86487 ________________________________________ From: [email protected] [[email protected]] on behalf of Matt Elias [[email protected]] Sent: Wednesday, 3 November 2010 4:21 p.m. To: [email protected] Subject: [rrd-users] Get DS:MAX without MAX RRA I would like to display two data definitions on one graph, temperature and humidity. I would like to get the main Y axis (temperature) scale to remain automatic (or manually set a little lower than the min and a little higher than the max) and the right axis (humidity) scale at the same scale (ie 0 - 100). My initial thoughts are that if I can get the graph's min and max temperature values, then maybe I can use that to scale the Y axis and use a formula to scale the humidty values accordingly so that they match the right axis' 0-100 scale. The min and max values I need are similar to the MAX and MIN values that are displayed in the GPRINT paramenters: "LINE1:Temp#32CD32:Temperature C", "GPRINT:Temp:MAX: Max\\: %5.1lf %s", "GPRINT:Temp:AVERAGE:Avg\\: %5.1lf %s", "GPRINT:Temp:MIN:Min\\: %5.1lf %s", "GPRINT:Temp:LAST:Last\\: %5.1lf %s\\l", If something like this is not doable from within RRDtool, then I may log additional data to a log file and have my graph generating perl script use that log file to manipulate the Y axis scales. Matt _______________________________________________ rrd-users mailing list [email protected] https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users _______________________________________________ rrd-users mailing list [email protected] https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
