Extended precision variable declaration in formula node?

I'm looking for a way to define my variables inside my formula node as extended precision but everytime I attempt this, I get an error. To my understanding, the declaration should be "long double" but it does not seem to work. Anyone have any ideas?
Greycat

Thanks Dennis ... I guess sometimes it seems quicker to ask instead of looking... but then I found what you were referencing very quickly. Just being lazy I suppose!!! Anyway, thanks for the help.
Greycat

Similar Messages

Precision of formula node?

I need to calculate a simple formulae.
But different results between two program.
Can you check which one is correct using other program?
or tell me the principle of calculation with formula node?
Enclosed is the example.
LabVIEW: 8.0614613965
Excel: 8.0614616898
-labmaster
Attachments:
excelexam.xls ‏584 KB
LabVIEW exam.vi ‏7 KB

If you do all the calculations in regular LV functions rather than in the formula node, you can use Extended Precision data types. That changes the 17th digit right of the decimal point.
When I look at the data at intermediate steps (the individual terms summed to get e_ITS90) I see that the spreadsheet matches to 7 to 13 significnat digits, depending on the exponent. Note that for the third term (with exponent = 0), the spreadsheet calculation does not return the g2 coefficient: g2 = 19.542636 and g2*x^0 = 19.54263612. I set up a column in the spread sheet with the values equal to the g[i] coefficients but displayed with as many digits as the spreadsheet allows. g1, g2, and g3 differ from what is entered in column C in the first several digits to the right of the last digit entered. When I do the same thing in LV, the differences tend to be in the 15th or 16th digit.
All of these things are the result of the way numeric data is represented in the computer, as Jeff pointed out earlier. It appears that you can get somewhat more precison in LV than in the spreadsheet. I did not do any accuracy checking.
Lynn
Attachments:
LabVIEW exam.2.vi ‏11 KB

How to difine global variable in Formula node?

I want to access the same vailable in different formula nodes, so I need to define a global or external vailables? How can I do this?

Formula Nodes are distinct environments from each other. You will have to define the global constant in each node. Or make it a variable and wire your values to the variable input node on each of the formula nodes.

I need in Formula Node to assign to the variable value 4000000000!!! What kind of variable it should be???

i've just tryed to write unsigned in32, but it does not understand 'unsogned'... But i need variable to be unsigned, because the max value = 4000000000... So, how can i solve this probleme???

Hi,
I don't see exactly what you're trying to do here.
Where do you want to assign the variable 4000000000 to? If you want it as an
input, just use a dbl, with only zeros behind the coma.
Note that an integer is a number without any decimals. An integer in LabVIEW
is this, but with an extra limitation that it can only be 32 bits... So a
dbl can be an integer.
If the input dbl is not an integer, use round, round to -inf or round to
+inf to make it one. This can also be done if the output needs to be an
integer.Inside the formula node floor(x), int(x), intrz(x) or ceil(x) can be
used to make integers.
I hope this is what you mean... I can't see any problems doing this.
Regards,
Wiebe.
"DrON" wrote in message
news:506500000008000000E
[email protected]..
> I need in Formula Node to assign to the variable value 4000000000!!!
> What kind of variable it should be???
>
> i've just tryed to write unsigned in32, but it does not understand
> 'unsogned'... But i need variable to be unsigned, because the max
> value = 4000000000... So, how can i solve this probleme???

Static variable in Formula Node

Hi,
How do I declare and use a static int variable in a formula node?

Hi splee,
You can look at Formulat node Syntax
Thanks as kudos only

Formula node forbid to run VI when undefined variable is used

On all LabVIEW version, we can use Formula node to evaluate mathematical formulas.
We can define input and output variable freely and calculate using some variety of formula.
But when we use undefined variable as output, can execute VIs with no errors.
We think it is a problem because when programmer makes a typo, they cannot notice the mistake.
When undefined variable is used as output variable, LabVIEW should forbid to run VI.

I think you are going to get the same (or similar) answers than to my suggestion(s) to make VI outputs potentially "required" and the same for some functions (built-in VIs):
http://forums.ni.com/t5/LabVIEW-Idea-Exchange/Allow-required-outputs-in-VIs/idc-p/3157058
http://forums.ni.com/t5/LabVIEW-Idea-Exchange/quot-Function-terminal-not-connected-quot-detection-plus/idi-p/1858573
In general, I agree with you, there is a potential for problems. Not really for the reason you are mentioning, because a typo will break the VI (unless you have two output variables with very similar names - unlike in your example - such as y and y0). But it could make for some frustrating debugging session.

Formula node with global variable

Hi,
I am tring to use formula node with global variables as an input and output,
but this is where I see the SW hangs forever.
By the way I am a novice to the labview.
Can some give me hint why this is happening?
Thank you in advance,
Do
Solved!
Go to Solution.
Attachments:
formula_node_wGlobalInputOutput.JPG ‏281 KB

Well, the first case of the two loops has a direct LabVIEW translation like this:
However, just because that's the direct translation doesn't mean that's what you should be doing. In the formula node it seems as if you were copying elements from one array to another. Element-wise operation on arrays via loops can be quite inefficient in LabVIEW. Often one can operate in place with arrays, and an operation that would require two loops in a language like C would actually require no loops in LabVIEW. In fact, with the above example, even if you were to use loops, arrays can auto-index for-loops so you don't even need to wire the constants to the N terminals to tell the loop(s) how many times to run.
Can you describe what you're trying to accomplish? There's likely to be a more natural way to do it in LabVIEW that would require no loops. Have you gone through the tutorials? You can also look over the material in the NI Developer Zone's Learning Center which provides links to other materials and other tutorials. You can also take the online courses for free.

Formula node does not accept complex variables

Is there any way to make formula node accept complex variables. I do not talk about dividing it to Real and Imag, but to have genuaine complex as an input.
thanks in advance
Pawel

Available data types are given in the following document:
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/d6bed7d73659c43586256a7300691c26?OpenDocument
MTO

Formula node output variable

I have a formula node with an output variable. When i run my program the first time the output is correct. But when i run it after that, only the previous output value is displayed, the variable is not refreshing. It seems as if the value is copied into the memory and is not being updated. Is there a property for the output variable that must be changed?

The formula node should update the output each time it is run. There is no property node for the ouputs.
Ensure that (1) your inputs are actually changing as you expect - use a probe to confirm and (2) that the indicator you are looking at is wired to the output correctly.
Post an example of the problem you're seeing if you still have a problem
Tim

Formula Node variable assignment problems

I have a formula node with the follwing:
Inputs:E,X,T,PD,I
OutputsK,PD
The statement inside the formula node is:
if (Eelse if (PD=1) if (E else if (E<=X) ;
else PK=I, PD=1;
The logic seems to be working the way I want, the problem is in the last else statement. PK is never assigned the value of I. however, PD is assigned the value of 1. There are no errors indicated.
The source of the I input is the iteration # of the For loop where this formula node is located.
Anyone see what I am missing??
Thanks,
Mike

Mike,
In comparisons, == should be used instead of =. This is a very common mistake, and a reason that forumla nodes should be avoided if possible (except of course for very long formulae that would require a lot of nodes.
It looks like your code would be better represented with LabVIEW nodes instead of in a formula node (for readability - there is no performance difference.)
Also, you may wish to reconsider using an Input variable that has the same name as an output variable. Try using PDi and PDo, or PD1 and PD2 instead.
Good luck.

Formula node uotput variable

If i use two different formula nodes with the same output and input variable names will the variables (scope) be the same? In the first formula node i define a variabe "int32 first ==0" then in a seperate node embedded in a for loop structure I write " if(first==0) first = chan;". That way the variable "first" is set equal to "chan" only once through all acquisitions of the for loop b/c "first " only equals 0 at the beginning of the loop. My problem is that after running the program more then once the value of "first" remains the same regardless of the new value of "chan".

I believe that the variables are local to the formula nodes themselves.
Therefore, in your first formula node, first is set to 0. In the second, if you don't define an initial value, it is assumed zero. So the first time through, it will get set to the value of chan. But the second time through, it already equals chan in the second formula node (not reset by the first formula node--they are separate variables). Therefore, it will never go to a new value of chan until it is reset to 0.
Mark

Eval Formula Node variable names

I am using the Evaluate Formula node to allow programatic changes to formula
in my data acquisiiton VI. Has anyone built any code to enable using full
descriptive names as variables, instead of the a0 to z9 that this VI limits
you to?

You can replace full decriptive names with short names like a0...z9 using Substitute Variables.vi, which you will find at 'Mathmatics'->'Formula'->'Advanced Formula Analysis'.

Array output from formula node with input variable as array size

Hi,
I have created a formula node with an array output called al, but I get an error "you have connected a scalar type to an array with that type".
I declare the output as follows..
float64 al[len_as];
where len_as is an scalar input to the formula node.
It only works when I put a number as.
float64 al[5];
,but I don't know beforehand how many elements I need, so I cannot use this.
Please help! This is so stupid.
Thanks

Don't define your array in your formula node.
Initialize the array as the size you want and pass it in as an input into the formula node.
Are you sure you even need to use a formula node? Can you implement your formula using all native LabVIEW functions?
Message Edited by Ravens Fan on 10-07-2009 11:51 PM
Attachments:
Example_VI_BD.png ‏3 KB

How a can restar all my variables of some "Formula nodes"?

I have one formula node with several outputs,
I want restar one of her value to 0 when one sentence is false o is true.

I am not quite sure what you are wanting to know. I suspect that you want to be able to write if-then statements (conditional ) in the formula node. The best place for this kind of information is to right click on the boarder of the formual node >> help.
I dug around for a few seconds and found the following cryptic information:
The numeric value of TRUE is 1, and FALSE is 0 for output. The logical value of 0 is FALSE, and any non-zero number is TRUE. The logical value of the conditional expression
is if the logical value of is TRUE and otherwise.
I think this means if is true then do otherwise do
There is an example that might be more helpful. Open LabVIEW >>
help >> find examples >> click on search tab >> look for formula >> open calculate volume.vi .

Formula node: type conversion

Hello guys
I have LV 5.0 and have to edit a script which has some kind of overflows. For testing I set all variables to the hightest usable range - extended or i32. Now I see, in all formula nodes, there are type conversions. How can I change the type of the inputs/outputs of the formula node?
Hardware_Tester
My first language is German, please ignore my faults...

Hi,
I forgot that you run Lv5.0. My example refers to Lv7.1.
As far as I know in Lv7.1 the input variable type changes automatically as you connect a control.
On the contrary the output is DBL by default but you can change it in the formula node introducing an explicit declaration of that variable (see "h" in the attached picture).
Here are some useful link:
http://forums.ni.com/ni/board/message?board.id=170&message.id=12253&requireLogin=False
http://digital.ni.com/public.nsf/3efedde4322fef19862567740067f3cc/d6bed7d73659c43586256a7300691c26?
Sorry, I understand that this cannot solve your problem but I don't remember how Lv5.0 works with formula node.
Regards
CLD - Labview Certified Developer
Attachments:
untitled3.gif ‏42 KB

Extended precision variable declaratio​n in formula node?

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Extended precision variable declaration in formula node?