how to add cursors on waveform chart

[mom]

how to add cursors on waveform chart as per waveform graph

falgandha

[altenbach]

Charts don't have cursors. You could use a graph and do all the chart logic (history buffer, x0 adjustment, etc.) in code.

[mom]

 i was not able to show data in waveform graph. please suggest any method to shoe cursor on waveform chart

[Riconquistiamola]

Hi falgandha,

altenbach is right to say charts cannot have cursors. This has been discussed in other discussion forum posts. Included are several workarounds.

Adding labels to a chart

Adding som kind of cursor in waveform chart

cursors on charts?

Trying to obtain cursors in a Waveform Chart

question---where to find the cursor palette?

etc.

Michael K. | Applications Engineering | National Instruments

[Cory_K]

I'm trying to think of the easiest way around this.

Do you think this would be relatively simple?

- Initialize an array.

- Add each line of data to that array.

- Graph that array on a waveform graph.

.... then I could have cursors

[altenbach]

---

Cory K wrote:

I'm trying to think of the easiest way around this.

---

Just built your history data in a shift register (or even the "collector" express VI), or do your own fixed size FIFO initilized with NaN, and then kep track of x0 accordingly.

Of course there is a reason that charts don't have cursors. one reason is the fact that you need to decide what should happen if the chart scrolls. Should the cursor remain with a given data point or be fixed at a certain axis offset? What should happen inf the cursor scrolls outside the history data?

[photonbridge]

One way to get the effect of the cursor without complicated programming is to use a horizontal pointer slide whose range is dynamically updated via property nodes to the x-scale of the waveform chart that you are monitoring.  The pointer uses the chart's history data (accessed also by property node) to select the point on the chart whose values you want to access and reads them out by indexing the historical data to the position in the array specificd by the pointer's value.  Visually this approach works particularly well if you place the horizontal pointer slide directly under the chart and adjust its length so that it matches the chart's x-scale.  Use the slide's property node to turn off itsvisible scale values since they are visible immediately above in the chart's x-scale.

[Raghu123]

Altenbach,

Here is my vi, I was trying to add a histroy for the graph similar to function like a chart,can you please let me know how to add a history buffer to a waveform graph, so that I can retrive the previous data latter.

[smercurio_fc]

Normally, you should start a new thread with your question since this thread was about adding cursors to a chart, and the note about history for graphs was a minor side-note. However, in this case you do not need to start the new thread since your question has been asked before. You can find an example here: http://decibel.ni.com/content/docs/DOC-4770

[Raghu123]

Smercurio_fc,

I was going through the vi in the link you gave me, but the vi is not maintaining any history. If I run the vi for some time, stop it and try to look at the previous data, i.e right from begining i couldnt retrive any old data. I dont know if iam missing anything. Can you tell me how to retrive the past data.