Chart recording[solved]
lazarus / 55-TAChart

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mica · 2015-12-07 22:39

Im setting up a Raspberry Pi with some DS1820 Temp Sensors.

Now i want to display last 24 h values with TAChart in a 6 h range
which is auto scrolling.

Is this easy doable or ist TAChart too complex and its easier to
handcraft the graph?

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wp · 2015-12-07 22:59

Shouldn't be a problem. Just ask here if you have difficulties.

Quote"Now i want to display last 24 h values with TAChart in a 6 h
range which is auto scrolling."Does this mean that the chart contains
always the last 24 hours and you only want to see the last 6 hours,
but you want to be able to scroll back to the beginning of the 24
hours? (You can use a TCharNavScrollbar to achieve this, for example).

What happens with data older than 24 hours? Are they dropped from the
chart?

At which time interval will you get the temperatures?

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fpcoder · 2015-12-08 00:17

Might not be the case, but if we assume that the data is stored in a
SQL database, TDBChartSource could be used for chart data. A SQL
statement like below could all the time provide only the last four
values for the chart:

Code: SQL  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i SELECT
temp_time, temp_valueFROM tempsORDER BY temp_time DESCLIMIT 4; --Or
variable parameter value from GUI

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mica · 2015-12-08 00:38

Quote from: wp on December 07, 2015, 11:59:02 pmShouldn't be a
problem. Just ask here if you have difficulties.

What happens with data older than 24 hours? Are they dropped from the
chart?

At which time interval will you get the temperatures?

yep data is not important its only plotting the graph.
i think of something like a round robin with a self scrolling  6h
"window" displayed.
Interval is 5 min at the moment.

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wp · 2015-12-08 11:59

In the attachment you find a possible solution (out of many others)
how you could achieve what you want. The form contains a timer which
creates pseudo-temperature values at 1 second intervals - I reduced
the interval from your 5 minutes in order to see an effect while
running the program. The program collects all data during 20 seconds,
when this not enough any more older values are dropped. It uses a
ChartNavScrollbar to display only the most recent 10 seconds and to be
able to scroll back to older values. Please note that the visible
window is always moved back to the most recent data value whenever new
data arrive - in the demo's 1 second data arrival rate it may be too
difficult to navigate through the entire 20 second data interval by
using the scrollbar, but it is very easy with your 5 minutes interval.

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mica · 2015-12-09 17:56

sorry for the late reply

Thanks for the example it fits my needs, points me in the right
direction and saved me a lot of research time

one little question:
there was a DateTimeIntervalChartSource1.NiceLabelStart property
unknown to Lazarus 1.4.4
when was it introduced?

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wp · 2015-12-09 18:01

Quote from: mica on December 09, 2015, 06:56:09 pmthere was a
DateTimeIntervalChartSource1.NiceLabelStart property unknown to
Lazarus 1.4.4
when was it introduced?
Sorry, it was never added officially so far. I wrote the demo program
on my development installation of Lazarus where I had experimented
with the DataTimeChartSource some time ago.