On Saturday 20 July 2024 at 07:42:39 UTC+10 [email protected] wrote:

I don’t fully understand the `line_gap_fraction` option. But I seem to 
remember that `None` values will always cause a break in the plot…


line_gap_fraction does seem a little mystical in operation but once you 
understand how it works it is fairly easy to use. Think of line_gap_fraction 
as the proportion of the overall x-axis timeframe that the plot engine 
considers to be a gap in data. So for a typical day plot (27 hours or 97200 
seconds) a line_gap_fraction of 0.05 means that any gap in time between 
successive plot points of 4860 seconds (81 minutes) or longer will be 
considered a gap and result in a gap in the plotted line. If line_gap_fraction 
= 0.01 the gap drops to 16.2 minutes. So for data with a 15 minute archive 
period a line_gap_fraction = 0.01 will plot a continuous line provided 
there are no missing points. Any missing points result in a gap of at least 
30 minutes so line_gap_fraction = 0.01 will result in gaps. In this case a 
line_gap_fraction 
= 0.02 or greater is required. The default line_gap_fraction = 0.05 should 
work fine. If it is not then something else is amiss (first thing that 
springs to mind is the possibility that line_gap_fraction is being 
overridden somewhere in the respective skin.conf or weewx.conf).

The same applies for week, month and year plots, but you now apply 
line_gap_fraction to a much longer overall x-axis timeframe meaning the gap 
in seconds for a given line_gap_fraction value is greater . Also, week, 
month and year plots by default plot an aggregate so the data points are 
now spaced every 'aggregate interval' seconds and not necessarily every 
'archive period' seconds.

Also, when line_gap_fraction is omitted (or set to a value <0 or >1) any 
missing data points will be considered a gap and plotted as such. In this 
case you definitely do not want to omit line_gap_fraction or you will 
always have gaps.

Gary

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