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  daylight saving and chartTime functions
Posted by Margherita Vittone on Mar-19-2011 00:24
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Hi,
we have been using ChartDirector to plot data coming from postgres database.
We have been using chartTime2 to represent dates.  After daytimesaving happened,
data show gaps with no data around the time the change occurred; is there
a workaround provided in the api?  We use python on linux machine.
thanks
Margherita

  Re: daylight saving and chartTime functions
Posted by Peter Kwan on Mar-19-2011 02:24
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Hi Margherita,

Whether there will be gaps in the chart depends on the type of chart you are plotting and the type of axis scale you are using.

For example, suppose you are using a real data/time axis, and you data points are at on a certain date is at [00:00, 01:00, 02:00, 05:44, 08:32, 11:33, 16:40, 22:00]. There is no way to know for sure if there is any gap in the above data (no matter there are DST or not). If you are plotting a line chart, it probably will not have gaps, but the data points will be unevenly spaced on the chart. If you are plotting a bar chart, depending on the bar width, there may be gaps between all bars, with wider gaps in some positions.

On the other hand, if you are using a label based axis (configured using Axis.setLabels), all data points will be treated as evenly spaced, regardless of the actual date/time. In this case, for a bar chart, all bars will be evenly spaced, with the gaps between the bars the same for all the bars.

If you need further help, is it possible to attach a chart image to help me understand the chart type you are using, and also how do you determine that there is a gap? (Are the data values always supposed to be evenly spaced in time, so any unevenly spaced points will become a gap?)

Regards
Peter Kwan