Francois Normandin

Hello Roy,

Welcome to the LAVA community.

You'll find that the level of LabVIEW awareness is pretty high here. Some will call it a good signal-to-noise ratio... Having been around for a short while, I can certainly testify that these pages are addictive!

Hope you find lots of good things to improve your skills.

Awesome.

However, if it's going to be put on the t-shirt, there shouldn't be a broken arrow...

QUOTE (JFM @ May 28 2008, 01:29 AM)

Hi prads,

it is always easier to get good answers if you can post a picture, or a piece of code, to show us what you have done.

If you want the bits to be written on the next row, add a newline '\n' at the end of the timestamp.

Appending data to a file does not require the Set Write Position to explicitly tell LabVIEW to append the data at each write operation, it is only necessary to do this before you start writing data to the file.

Hope this helps

/J

Indeed, each time you append some data to file, the "Set Position" will be at the end of what you wrote. If that was at the end of the file, you'll still be at the end of the file without any need to specify it. You can use the "Set Position" VI when you want to change some data in a file without rewriting all of it (changing a status bit or else...).

Also, you might want to save your bits as a number instead of text "01010101". Your code & file will both be more compact, and it's easy to convert back to array of bits if needed. See attached picture.

http://lavag.org/old_files/monthly_05_2008/post-10515-1211978264.jpg' target="_blank">

EDIT: It took me too long to write! Justin beat me to it... :-)

You need to convert types to be compatible with the datatype accepted by the write.vi (or any VI for that matter). If you choose "string" as your paradigm, then convert everything to string and concatenate in a format you want (tabulated, coma-separated values, custom, etc.) Then write to file. Browse through the palette for "string" manipulations. You will find many fonctions to help you do just that. LabVIEW tutorials and help file contain many examples to get you started with.

If you want more specific help, you should show us what you've done so far by uploading a VI with your best effort or posting a picture of your block diagram.

QUOTE (prads @ May 20 2008, 09:12 PM)

Hello,

I have a few doubts in labview......

1. I have a reference out as the output of a Property Node. Is it possible to write this into a text file? I tried but it gives errors stating that output is reference(output of Property Node) and input is string(Input of a write to a Text File). If yes how? Also I have another important question regarding this. In a Property Node, after setting several properties, does the output of the property node, called the reference out, contain all the set properties in a particular fashion or is there any other explanation for that? Im kind of confused with that. In the sense does a Property node act as a node/Mux which takes in several properties as input and outputs a single value? I want to write the output of this Property Node (The properties that I set in the Property Node initially are a mix of double and Integer data values) to a text file which when opened should have all the values of the properties displayed as set initially....

Hi there. It seems you confuse the reference out (which is really just a pointer if you're used to text programming) with the actual properties of the control or indicator.

Have a look a the wiki for Control References: http://wiki.lavag.org/Control_References

http://lavag.org/old_files/monthly_05_2008/post-10515-1211334833.jpg' target="_blank">

QUOTE (Choumann @ May 10 2008, 10:52 AM)

There is just one last thing I need to do now, and that is to write an acquired geometrical number to a file. I can write for a single image, but not for an entire avi.

I get this error message:

Error 10 occurred at Open/Create/Replace File in IPWD.vi

Possible reason(s):

LabVIEW: Duplicate path.

=========================

NI-488: New I/O attempted with old I/O in progress.

The error I get when running your code dissapears when you switch "Create" to "Open or create". Although there was a missing subVI and I can't be sure that was your real problem. If you want to append data to the same file over and over again, then that would explain the error you got with "Create" attribute.

You should take a look at some of the examples in LabVIEW's search engine under Fundamentals/File Input & Output. There are some nice examples on which you can rely for what you want to do.

QUOTE (Choumann @ May 9 2008, 06:19 AM)

Error -1074396080 occurred at IMAQ Extract Single Color Plane

Invalid image type.

Possible reason(s):

IMAQ Vision: (Hex 0xBFF60450) Invalid image type.

Hi Choumann,

To extract Intensity plane, you need to have a HSL 32-bit, RGB 32-bit or RGB 64-bit image. You will get an error if you acquire a grayscale image.

Check the image type you're acquiring like shown here:

http://lavag.org/old_files/monthly_05_2008/post-10515-1210335436.jpg' target="_blank">

If that's not the problem, could you post an example of the image you're trying to process (in jpg or png format)? I don't have any cameras attached to my PC at the moment...

QUOTE (Karissap @ May 8 2008, 02:33 AM)

If you just care about the type of data including differentiating the type of numeric DBL, I32 etc have a look at the http://wiki.openg.org/Main_Page' rel='nofollow' target="_blank">Open G VI "Variant to Header Info". See the attached front panel and block diagram.

OpenG :worship:

QUOTE (cmay @ May 5 2008, 07:39 PM)

Continuing on this topic... is there a property that tells which type of numeric the control is (i.e. whether it's an I32, DBL, etc.)?

If you haven't changed any default values for limits, you could use the "Data Entry Limits" property to determine which datatype by correlation with expected value for each datatype, but I don't think there is a direct way. Maybe there is something accessible with VI scripting (see Rusty Nails forums), but I haven't found it yet...

@Guenther:

Your code works good, but I now found an even easier way, it is possible to use a cursor and set it to snap to all plots. So you can just move the cursor and it will snap to the nearest plot and show its name. Thanks anyway!

Download File:post-10515-1209047068.vi

Hi Osiris, hope this helps...

PS: Credits to Guenther for his use of "Invoke Node: Map Coords to XY"... I learned the hard way there was actually an easy way to do this (while formula node is nice, it took me quite some time to do the same trick!)

QUOTE (Justin Goeres @ Apr 22 2008, 08:57 PM)

Here's another whack at it, with a bit less duplicated code. It also trims the two extra linefeeds at the end, for those who are counting .

markermovement.pdf

Attached VI:DyRASS.vi

I sure like this one best so far... I think it's very tight coding! :thumbup:

QUOTE (PaulG. @ Apr 22 2008, 01:42 PM)

(sniff) LabVIEW is "wonderful" and "exotic". (sniff)

Although the 3 stars are truely disappointing... I guess that's to be expected from non-G believers.

Anybody has a HTML version of this:

"99 bottles of :beer: on the wall, 99 bottles of :beer: .

Take one down and pass it around,

98 bottles of :beer: on the wall.

98 bottles of :beer: on the wall, 98 bottles of :beer: .

Take one down and pass it around,

97 bottles of :beer: on the wall..."

Download File:post-10515-1208902763.vi

QUOTE (orko @ Apr 10 2008, 06:33 PM)

Perhaps an even bigger clue is the fact that your MCL is an integer and his is an array of integers...

It does take care of the coercion dots but putting both of them "Scalar" doesn't solve the problem that the icons are not displayed on the second column of the left listbox...

QUOTE (tcplomp @ Apr 10 2008, 02:48 PM)

I can't easily spot the difference.

Well, I can't say there is a difference either. I can even reproduce your error!

I compared a new MCListbox with the one in PJM's VI and I get two different results...

I can see from the coercion dots that they're not the same type. That seems a clue. However, I haven't found yet what's the difference. Hopefully, a good night of labview dreams will get me on track.

Download File:post-10515-1207863359.vi (version 8.5)

I think you're looking for a master/slave or producer/consumer designs.

Check out the templates that you can access when selecting "New..."

You can get your inspiration from one of the templates you'll find there. (see picture)

QUOTE (Norm Kirchner @ Apr 4 2008, 11:45 AM)

Sure I could come up w/ my own, but wouldn't it be great if the whole community came up w/ a common consesus on what kind of object wires should look like whatever.

example: LVOOP w/ references should use the chain link style wire, and all parents should use a black border, etc...

Any ideas?

Anyone already have their own they care to share?

I agree with Norm. Just like Justin, I usually choose a wire color similar to the banner and mix with high-contrast colors when I'm using yellow or other light colors. But since I don't have a real systematic way of looking at it, I support this discussion before we all develop in mixed directions and become too conservative each about our own way to agree on a real practical "good wire design practices". If NI wants to see what's our reaction, well let's indulge them... since I won't have the privilege to have a paid trip to NI Week.

One thing I tried and let go quickly is using large size wires (5+ px) or even size (2, 4, 6, 8px). I don't know, it might be that I don't have any imagination, but I can't seem to be able to create a nice-looking 4-pixel wide wire! So I'm stuck with 3/1 or 1/1 configuration. Any suggestion here would help! And don't refer me to Bezier-style wires... :laugh:

One idea for colors could be to propagate the major color of a Parent Class to the Child Class (Parent's Edge foreground becomes its Child's Edge Background & Center foreground. A grandchild class would then look less its grandparent than it does its parent class... and so on.

http://lavag.org/old_files/monthly_04_2008/post-10515-1207367911.jpg' target="_blank">

QUOTE (Aristos Queue @ Mar 19 2008, 03:14 PM)

What are you trying to build?

It was only a theoretical question. I thought I could build a superdriver for instruments I have in my lab, for example something that would call VISA, IVI or AI transparently. But I don't want something more complicated for me than it will be for the user... I think I'm asking for a small change that would have made my life easier in this situation but would inevitably complicate the task of everyone else!!!

QUOTE (Aristos Queue @ Mar 19 2008, 03:14 PM)

Well, now it does. I didn't realize I was asking for Private Data Override. Thanks Justin for pointing that out...

In this particular example, I could have the parent class contain a complex number as you suggested: any DBL value I'd wire as an input would be coerced to the form x+i*0, so I wouldn't lose any data/precision. For directory, I'd better use a string than to play around with type overrides.

QUOTE (Aristos Queue @ Mar 19 2008, 03:14 PM)

What are you trying to build?

It was only a theoretical question. I thought I could build a superdriver for instruments I have in my lab, for example something that would call VISA, IVI or AI transparently. But I don't want something more complicated for me than it will be for the user... I think I'm asking for a small change that would have made my life easier in this situation but would inevitably complicate the task of everyone else!!!

QUOTE (Aristos Queue @ Mar 19 2008, 03:14 PM)

Well, now it does. I didn't realize I was asking for Private Data Override. Thanks Justin for pointing that out...

In this particular example, I could have the parent class contain a complex number as you suggested: any DBL value I'd wire as an input would be coerced to the form x+i*0, so I wouldn't lose any data/precision. For directory, I'd better use a string than to play around with type overrides.

QUOTE (Aristos Queue @ Mar 14 2008, 10:47 AM)

I believe the solution in your situation is

a) Make the output terminal be of the Parent class type and

b) do not make that output terminal "dynamic dispatch output".

The dynamic dispatch input must preserve data type from input to output, and so must be the same class as the input. But a regular output is free to output any value of the output type, which, since the output will be some type of Parent, can be any child type you want to change to.

Is this what you're looking for?

I tried what you're describing and it doesn't seem to work. If I wire the Parent type class as the output, I cannot call the child VI anymore as it won't propagate the child class to the next input, however dynamical these inputs. I'd have to cast to a more specific class and that removes the advantage of dynamic dispatch. For now, the only solution I see is to use variants, which is fine if that's the only way...

There also the problem that broken arrows are not gone. I'd have to remove inheritance because the connector panes don't match. Yeap, variants will have to do.

http://lavag.org/old_files/monthly_03_2008/post-10515-1205762115.jpg' target="_blank">

QUOTE (eaolson @ Mar 14 2008, 11:15 AM)

Would (b) prevent you from overriding the VI in a grandchild class? I should probably know the answer, but I have not had the chance to work with LVOOP as much as I'd like.

Yes indeed, it would work if there are no more overrides to be done, which makes it a dead-end for future speciations. In the case I present it would still be a good compromise, since my instrument.model class would most probably be the end of the line (instrument = parent; model = child w/o any possible grandchild)... Which would make it a "sterile class" by not being able to reproduce. :laugh:

Thanks all for your inputs.

I thought about starting a new thread but somehow I thought the title of this one applied nicely to my question too. So here it is.

I'm trying to use override functions to change the datatype from ancestor to child class. My motivation is that for instrument driver, we sometimes have different types (VISA, strings, IVI, ...) and I would like to have all derive from the same ancestor class (say instruments.lvclass). I was surprised to find out I could not change the datatype. I get the error saying the connector pane should be the same, so I had to go around the problem by using a Variant and all the subsequent dealings associated with that.

I made a simple test using Numeric and Directory in an ancestor class (DBL Numeric + String Directory) for which I override with a Complex Numeric in one case and a Path Directory in the second case. I'd like to know if it is even possible to imagine such a feature working correctly in LVOOP? Why is this diagram giving me a broken arrow? I am not used to OOP in C++ or other languages but I thought it was something possible in C++...

Could that be solved with dynamic dispatch for controls/indicators other than Objects? For the moment, I saw this possibility is grayed out...

By the way, all connector panes are the same, except datatype...

Hi Georges,

Eight solutions. Here are solutions for the four (x,y) couples. Then resolve r for ± signs in the original equation: (x-x1)^2 + (y-y1)^2 - (r±r1)^2=0 to get the other four solutions.

x1 = [2(y1-y3)(x1^2+y1^2-r1^2) - 2(y1-y2)(x3^2+y3^2-r3^2) - 4(y1-y3)(r1-r2)r + 4(y1-y2)(r1-r3)r ] / [ 4(x1-x2)(y1-y3) - 4(x1-x3)(y1-y2) ]

y1 = [-2(x1-x3)(x1^2+y1^2-r1^2) + 2(x1-x2)(x3^2+y3^2-r3^2) + 4(x1-x3)(r1-r2)r - 4(x1-x2)(r1-r3)r ] / [ 4(x1-x2)(y1-y3) - 4(x1-x3)(y1-y2) ]

x2 = [2(y1-y3)(x1^2+y1^2-r1^2) - 2(y1-y2)(x3^2+y3^2-r3^2) - 4(y1-y3)(r1-r2)r + 4(y1-y2)(r1-r3)r ] / [ 4(x1-x2)(y1-y3) - 4(x1-x3)(y1-y2) ]

y2 = [-2(x1-x3)(x1^2+y1^2-r1^2) + 2(x1-x2)(x3^2+y3^2-r3^2) - 4(x1-x3)(r1-r2)r + 4(x1-x2)(r1-r3)r ] / [ 4(x1-x2)(y1-y3) - 4(x1-x3)(y1-y2) ]

x3 = [2(y1-y3)(x1^2+y1^2-r1^2) - 2(y1-y2)(x3^2+y3^2-r3^2) + 4(y1-y3)(r1-r2)r - 4(y1-y2)(r1-r3)r ] / [ 4(x1-x2)(y1-y3) - 4(x1-x3)(y1-y2) ]

y3 = [-2(x1-x3)(x1^2+y1^2-r1^2) + 2(x1-x2)(x3^2+y3^2-r3^2) + 4(x1-x3)(r1-r2)r - 4(x1-x2)(r1-r3)r ] / [ 4(x1-x2)(y1-y3) - 4(x1-x3)(y1-y2) ]

x4 = [2(y1-y3)(x1^2+y1^2-r1^2) - 2(y1-y2)(x3^2+y3^2-r3^2) + 4(y1-y3)(r1-r2)r - 4(y1-y2)(r1-r3)r ] / [ 4(x1-x2)(y1-y3) - 4(x1-x3)(y1-y2) ]

y4 = [-2(x1-x3)(x1^2+y1^2-r1^2) + 2(x1-x2)(x3^2+y3^2-r3^2) - 4(x1-x3)(r1-r2)r + 4(x1-x2)(r1-r3)r ] / [ 4(x1-x2)(y1-y3) - 4(x1-x3)(y1-y2) ]

QUOTE(eaolson @ Mar 6 2008, 10:16 AM)

Oooh, three circles is much harder. If you want an exact solution, it's not straightforward. It sounds like you're talking about http://mathworld.wolfram.com/ApolloniusProblem.html' target="_blank">Apollonius' Problem.

:worship: I think I'm not worthy!

QUOTE(george seifert @ Mar 5 2008, 02:47 PM)

I think I see how your sketch works with two circles. The center of the encompassing circle has to lie along the line between the two circles, right? I have three circles that I have to encompass and I'm not sure how your method would work in that case.

George

I guess you could iterate eaolsen's solution. Select any two circles of yours and find the circle that encompasses them both. Then repeat using this intermediary solution with your third circle should give a final circle encompassing the three circles. It could even work with "n" circles.

QUOTE(eaolson @ Mar 4 2008, 04:47 PM)

I don't think normandinf's solution will work, exactly. If you consider the case where R2 is smaller and entirely contained within R1, then the containing circle is obviously centered at (x1,y1) with radius r1. But (xc, yc) != (x1, y1). So you get a circle of the right radius at the wrong location.

I somewhat agree with this, except that it was my understanding that the circles are representing the irregular-shaped mass. In such a scenario, Vision will not give a circle completely inscribed in the others...

***EDIT***

Hummm, I think I made an other mistake... Maybe I should rethink again. It seems there's also a problem using cardinal points...