topic Re: Add values to array by clicking in LabVIEW

Add values to array by clicking

Cory_K — Fri, 10 Oct 2008 19:57:19 GMT

Well I thought of a pretty cool VI conceptually, but I can't figure out how to actually execute the code.

I have data that is read from a file, then graphed on an X-Y graph. I have a cursor that displays the x and y values of the current point.

I would like to do the following:

Have an initialized array. Then I manually move the cursor to a point of my choosing, then click a button.
That button will make the x and y value of that point append to the array. Is this possible? Or more importantly, how?

Thanks,
Cory

Re: Add values to array by clicking

smercurio_fc — Fri, 10 Oct 2008 20:06:22 GMT

Almost anything is possible.

What you're asking for is actually quite easy. To do what you want you need to respond to the graph's MouseDown event and then use the graph's Max Coordinates to XY method to get your XY pair. This method will also tell you if you clicked on a point, rather than, say, on the legend.

Re: Add values to array by clicking

Cory_K — Fri, 10 Oct 2008 20:11:56 GMT

Smercurio, in your example, what is controlling the boolean in the while loop?

It appears that I can only enter a data point once and then the loop stops. Or is that not correct?

Re: Add values to array by clicking

smercurio_fc — Fri, 10 Oct 2008 20:18:50 GMT

There's a Stop button on the front panel, and I have a case that handles the button's Value Change event. A fairly standard way with event structures.

Note that the example is a crude, quick-and-dirty one just to get you started. An Issue that you would need to consider is how far away you clicked from the actual curve. The method I showed will return the nearest point, even if you clicked a point that you may consider to be "far away" from the curve, but still within the graphing area. You may, for instance, only want to add the point if you basically clicked right on the point.

Re: Add values to array by clicking

Cory_K — Fri, 10 Oct 2008 20:20:20 GMT

And I'm still pretty new with LabVIEW. Could you tell me where you found those properties for the graph.

I created a property node, but there are SO MANY properties, could you tell me the sub-heading under properties

where you found those.

Just trying to keep learning, thanks,

Cory

Re: Add values to array by clicking

smercurio_fc — Fri, 10 Oct 2008 20:24:37 GMT

It's not a property, it's a method. Remember, I said "use the graph's Max Coordinates to XY method". Right-click on the graph and select Create-> Invoke Node -> Max Coordinates to XY.

Attached is the VI done in LV 8.2.

Re: Add values to array by clicking

Cory_K — Fri, 10 Oct 2008 20:27:10 GMT

Oh, thats probably why I couldnt find that property, because it isnt a property.

Thanks for your help.

Re: Add values to array by clicking

Cory_K — Fri, 10 Oct 2008 20:32:13 GMT

When I create an invoke node --> method, I only have 5 methods to choose from,

none of which being the one you stated.

I have:

1) Attach Data Socket

2) Get Image

3) Get Term Image

4) Reinit to Drift

5) Remove Data Socker

Am I still doing something wrong?

(I can't open your VI because I am running 7.1)

Re: Add values to array by clicking

Cory_K — Fri, 10 Oct 2008 20:39:29 GMT

Since this topic in specific is pretty new to me, does anyone know of anywhere off hand I could learn about 'Methods'.

Like a hyperlink to some NI article or some forum thread or something?

I am self-taught at LabVIEW, so I try to pursue a topic if I don't know it too well.

Thanks

Re: Add values to array by clicking

Cory_K — Fri, 10 Oct 2008 20:58:14 GMT

Am I doing something wrong here? I can add the x and y value of the cursor once, then it just holds those values and wont let me do anything else?

Message Edited by Cory K on 10-10-2008 03:58 PM

Re: Add values to array by clicking

a_carollo — Fri, 10 Oct 2008 21:03:09 GMT

Try moving the property node and associated logic, along with the O2 boolean into the "mouse down" event case.

Message Edited by a_carollo on 10-10-2008 04:03 PM

Re: Add values to array by clicking

smercurio_fc — Fri, 10 Oct 2008 21:02:55 GMT

In LabVIEW 7.1 you have to do things a little differently. Yes, that method is not available in 7.1. I'm not sure what you're doing in your VI since I can't see the front panel to see what those buttons are. Normally if you have buttons you respond to the Value Change event and have the button in the event case so the event structure can read the value and update the control. If you post your VI I will be glad to take a look at it. I have 7.1 on a virtual machine.

Re: Add values to array by clicking

Cory_K — Fri, 10 Oct 2008 21:06:59 GMT

I moved the buttons inside their respective events, but to no avail.

I attached my (or shall I say mostly smercurio's) vi if anyone would like to take a look.

Re: Add values to array by clicking

smercurio_fc — Fri, 10 Oct 2008 21:23:15 GMT

Where are the O2 and N2 buttons? Also, what does your datafile look like? I'm trying to wrap my head around your array gymnastics.

I'm guessing you're trying to peel off one column for X and another column for Y. You can use Index Array to do this directly in one operation instead of using 4 different array functions for each column.

Message Edited by smercurio_fc on 10-10-2008 04:23 PM

Re: Add values to array by clicking

Cory_K — Fri, 10 Oct 2008 21:28:39 GMT

My data looks basically like a sine curve.

All the maximum peaks signify O2, and minimums N2.

The buttons should be right on the front panel. In the block diagram, they are inside the event structure.

As far as getting the x and y values into arrays.....don't worry about it, I taught myself LabVIEW so my methods are a little unorthodox 😉

I'll use your method next time.

I'll attach my updated VI and a sample file so you can run this bad boy.

Re: Add values to array by clicking

Cory_K — Fri, 10 Oct 2008 21:41:55 GMT

You know what, I attached the incorrect VI, sorry.

Give me a minute to attach the correct one

Re: Add values to array by clicking

Cory_K — Fri, 10 Oct 2008 21:58:35 GMT

OK here is my current VI

Message Edited by Cory K on 10-10-2008 04:58 PM

Re: Add values to array by clicking

smercurio_fc — Fri, 10 Oct 2008 22:36:35 GMT

Ah, so this actually has to do with this question. Have you tried simply using the Peak Detector function to get your peaks and valleys?

Re: Add values to array by clicking

Cory_K — Mon, 13 Oct 2008 19:53:21 GMT

Well I don't want the absolute relative peak (if that makes any sense at all) because the noise makes the peak slightly higher than it should be. This is why I would like to go through and pick out the peak myself.
That is the point of the VI (whenever I finally get it working).

I have the VI so each time I click, the value of the cursor will change, however it does not append to the table,

it just replaces the first value over and over.
Any thoughts as to why that is?

Re: Add values to array by clicking

Claire_Reid — Mon, 13 Oct 2008 21:00:07 GMT

Hi Cory,

I have slightly modified your VI, please let me know if this solves your problem.