On Sat, Sep 29, 2007 at 09:51:29AM +0200, Holger Rose wrote: > Hi! > > I work on a small alternative weather station diagram with rrd. In this time > i can display some values (temperature, rain ...), but with others i have > mental problems.
Rates, not values. As soon as you forget this, you will have a hard time understanding what's happening. It is OK if you "abuse" rrdtool to display other values, but you need to understand that what you are doing is somewhat a hack. Especially normalization is important to understand, if you are going to work with wind directions. If the wind direction is 350 at one moment and is 010 at another moment, and if you were not careful, there's a good possibility that RRDtool will eventually store 180 for one interval. That is not a bug, it is documented behaviour and is easy to understand as long as you keep in mind that RRDtool is about rates. A similar problem (for you, not for RRDtool) exists when you are going to consolidate data. If the wind direction is 350 during 5 minutes, and 010 during the next 5 minutes, and when you consolidate these two directions into an averaged value, you will get (350+10)/2=180. You could use LAST, or MAX, instead of AVERAGE but that's not really what you want. I haven't thought about this much yet, but I guess you should be thinking about splitting directions into north-south and east-west, let RRDtool do its thing, and combine the two at graph time. > When i will display Wind direction the graph should be see like the Wind dir > (deg) Graph in http://owfs.org/index.php?page=weather----owfsws (only a point > for each value). Is that possible? You could try a transparent area with a stacked line of width 2 at rate 0. Depending on the amount of pixel rows per interval, this may work. > In wind dir i would like to display a normalized average of the values as > additional graph (line as main wind direction). How can i do that? Maybe man rrdgraph_rpn and look for TREND ? > When i will draw Wind speed, the graph has a dropout when Wind Gust is there. > Is a mechanism in rrd who will delete values which are a lot greater or > smaller then the last value (dequeues spikes)? If so, (how) can i disable > this setting? No. But as soon as consolidation kicks in, you may want to think hard about how the maximum of a series of averages is quite different from the maximum of a series of maximums. Make sure you keep MAX RRAs as well as AVERAGE RRAs. You also may want MIN RRAs. -- Alex van den Bogaerdt http://www.vandenbogaerdt.nl/rrdtool/ _______________________________________________ rrd-users mailing list [email protected] https://lists.oetiker.ch/cgi-bin/listinfo/rrd-users
