[Kst] Real-time data display without files ?

Dirk Eddelbuettel edd at debian.org
Tue Apr 25 04:36:10 CEST 2006

Hi Barth,

Thanks for the feedback.

On 23 April 2006 at 23:07, Barth Netterfield wrote:
| On Sunday 23 April 2006 10:20, Dirk Eddelbuettel wrote:
| > Yes, but how would I get it loaded / started? I saw no command-line or menu
| > option for it ...  Can you give me a pointer as to where to start digging?
| In principle, you could write and install a datasource to do this.

Ok, I get the hint that this is non-obvious in terms of tieing it to the
existing UI.

| > edd at basebud:~> /tmp/kstdemo.sh | kst -x 1 -y 2 -
| Just keep in mind that all data hitting kst will be cached, eventually filling 
| up virtual memory.  I prefer to explicitly cache to disk with the logger, and 
| re-read from kst:
| edd at basebud:~> /tmp/kstdemo.sh > tmp.dat &
| edd at basebud:~> kst -x 1 -y 2 tmp.dat
| the file system will make sure that you never actually read from disk unless 
| you go back before things are buffered... so the performance is going to be 
| basically indestinguishable (sp).

Nice. I tried this at work today, and it works fine. 

New problem and question: can kst 'synchronise' separate sources? If I have
several data streams in different files coming at similar but not identical
rates and times, then the x-axes 'drift' apart and the simple equations I
plotted looked 'jagged'.  Do I have to synchronise this in the logging app
which writes the files for kst?

| kst can read a couple of very light weight binary formats designed for this.  
| If you decide to go binary, let us know and we can describe them.
| Remember, on each update, kst will only be reading the unread data; at a 20 Hz 
| aquisition rate and only a few vectors, this will be no trouble I would 
| guess.  We read dozens of channels at a 100Hz/channel aquisition rate.


| what is your data?

Fairly high frequency securities price data as well some related data.

Thanks again,  Dirk

Hell, there are no rules here - we're trying to accomplish something. 
                                                  -- Thomas A. Edison

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