Chart with 0/1 values also shows values in-between

Setup, Configuration and Use Runtime
1

Hi guys,

I am using a chart for showing my iPhone presence. The underlying script returns either 0 or 1 and so should the graph display either 0 or 1.

But oddly enough sometimes the graph shows values in-between:

chart.jpeg1289×647 89.8 KB

I have never noticed this behavior in OH1.

Is this a problem of the chart? Or the persistence (I am using rrd4j for the charts)? Or is there anything I can do against? Maybe I have to synchronize the refresh rate and the script execution (every minute)?

Any ideas are welcome…

Thanks,
Stefan

2

Can you check if this behavior is the same if you change the chart to e.g. one hour?
Maybe its a problem of the resolution?

3

It’s the problem of RRD. RRD uses only a limited number of values which are calculated to a mean value.
Please read about rrd4j persistence in the openhab wiki https://github.com/openhab/openhab/wiki/rrd4j-Persistence.
Older values are compressed to meet the goal of a not growing database. Therefore you get mean values for a certain period of time.

Andreas

4

Sounds logical. Thanks Andreas!