[Kst] X-axis time scale to match sample rate

Andrew Walker arwalker at sumusltd.com
Wed Oct 14 19:37:37 CEST 2009

Hi Ben,

There is no simple way but the following works well.
The basic idea is to create a equation that scales the INDEX vector by the 
desired sample rate and then plots the y-vector against this.

* Read in the data as usual
* Create a new equation: Data...New Equation...
* In the "New equation" dialog enter the following in the "Equation" field:
where <scale> is the desired sample rate (e.g. [INDEX]*5.0)
* Select "Do not place in any plot" and hit "OK"
* Create a new curve: Data... New Curve...
* For the "X axis vector" select the output of the new equation: 
"INDEX*<scale>/sv" (note that it is /sv and NOT /xsv)
For the "Y axis vector" select your usual y-axis vector
* Click "OK"

This should produce the desired result.


----- Original Message ----- 
From: "Ben Lewis" <ben.lewis at egretengineering.com.au>
To: <kst at kde.org>
Sent: Tuesday, October 13, 2009 7:57 PM
Subject: [Kst] X-axis time scale to match sample rate

>I have an application where I log data multiple times per second.
> Each line in the data file contains variable data only (i.e. no time
> data is recorded).  Time data is not needed as I know the test start
> time and the sample rate.
> When I read a data file into KST I use the option to "interpret INDEX as
> INDEX".  I then plot the variable data (y-axis) against the index value
> (x-axis).
> I would like to be able to plot test data on a time scale rather than an
> index scale.  I cannot see an option to enter the sample rate.  What is
> the  recommended procedure for doing this?
> Regards, Ben
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> Kst at kde.org
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