how to read x axis from chart???

[Bauch@Berkeley]

"Hello,
sounds easy but I did not find any answer yet.
I have a chart with 15 temperature values on the y axis and the x axis is real time.
I just try to read out the whole data in to a graph to work with the curves. But LV reads only the y values.

hope someone can help.

best regards"

[Dennis_Knutson]

In a chart or regular graph (not xy), the x axis is not an array of values like the y axis. You just need to use a property node and get xscale.offset and xscale.multiplier. You could wire up the values from the chart to a property node of the graph or create a waveform datatype from the y axis array and the chart's timing data.

[Bauch@Berkeley]

Hallo,

that is exactly what I need but how do I create waveform data type?
On the other hand I thought it might be possible to extract the x array like one can do in an x / y graph - like a secret feature 🙂

thx for help

[Dennis_Knutson]

You build a waveform datatype with the function Build Waveform on the waveform palette. It's just like a bundle by name. You can drag it or right click and select add items to create the inputs you need - y array, t0 (start time), and dt (time interval).

When you created the chart, there wasn't an x array that you wired to it was there? It doesn't exist and there is no secret feature to extract something that doesn't exist.

[Bauch@Berkeley]

Yes, but I think it should be possible, because it can not be such a problem to plot the x axis values to an array. But this is a deficit of LV.

I will try it your way and thanks.

[IanW]

Hi Bauch

If you need to get your X array see the attached diagram.

You need to be careful though, how was your original chart data created? Hardware timed data acquisition is OK but not always software timed. The chart assumes the data is built up at regular intervals, but this is not necessarily the case. I�ve had problems when I thought data was collected at a regular 10 scans a second and so I set the delta t to 0.1 s on the chart. In fact the data was only going in at 6 scans a second, and even this was not consistent. Looking at the chart history in this case gives an incorrect X array (as would a waveform data type).

Ian

[Dennis_Knutson]

It's not a deficit - it's a feature. If you want to transfer the data to a graph, you don't need an x array. If you want to create an x array for an xy graph or for a file, that can be done but it's not what you asked for.

[mstutz]

Hello,

I realize this is an old post and I'm using Labview 8, but I was still hoping someone would see it and that it is still relevant.  I am working on a similar problem I have a waveform chart coming from temperature data against time.  I can get a lvm file from it that says delta x (time) is 1.   I also have ran a get waveform time array vi and got the points 1, 2, 3, etc. Is there a way to prove that I am actually getting one measurement every second?  Also how can you tell if your data is hardware timed data or software timed?

Thanks a bunch.

[Rudi_N]

mstutz:

I would appreciate if you could provide me with more detailed information about your issue so that I can help you further.

Regards,

Rudi N.

[mstutz]

Rudi

Sorry took a while to get back to you.  I actually found a rate icon that feeds into my loop.  So I guess it is software controlled to just give me whatever data it has at the given time intervals.

Thanks