[Kst] plotting data in realtime: tips and tricks?

[Brisset, Nicolas]

Hi Timo,

> 

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-----Ursprüngliche Nachricht-----
> Von: Timo Juhani Lindfors [mailto:timo.lindfors at iki.fi]
> Gesendet: Freitag, 11. Juni 2010 00:43
> An: kst at kde.org
> Betreff: [Kst] plotting data in realtime: tips and tricks?
> 
> Hi,
> 
> I'd like to plot data from an AD converter in realtime (10000 16-bit
> samples per second, four channels). Using
> 
> read-data | kst -y 1 -y 2 -y 3 -y 4 stdin
> 
> works but configuring ranges for X axis seems to be tricky: I would
> like kst always show me the data that has been received during the
> last five seconds and not more.  I tried set range to "expression" and
> then used from range [P1/XMax] - 50000 and "to" range [P1/XMax].
I am not sure I understand what you are trying to do nor do I have experience with the stdin source, but I would simply check "count from end" and set the vector ranges to 50000 samples, either in the wizard (but I guess it does not work for stdin, and there does not seem to be a commandline switch for "count from end") or in the Tools -> Change Data Sample Ranges tool menu.
In the worst case, you could send the output to an ASCII file and read it with the ASCII datasource. It is probably not as good performance-wise due to the file I/O operations (unless you write on a ramdisk maybe?) but it definitely would allow showing only the last 5 seconds with scrolling curves.

Nicolas