Array Handling in Formula Node
I have attached a simple VI wherein I want to take an input array, look at its size and use the size of the input array as the size of the output array. The output array needs to be declared. I want to be able to use the size of the input array "N" as the size of the output array too. The size of the input array changes dynamically based on my simulation needs. I dont want to modify the size of the array in the declaration every time I change the array size in simulation.
I have tried using b[N] instead of b[10] in the formula node. However LV does not seem to accept this and gives me a syntax error.
Attachments:
Array Handling in Formula node.vi 8 KB
AGovi wrote:
However I require to use complicated formulas such as
If a simple formula is easier in G, a complicated formula will also be easier in G.
Actually, it will scale better. Since graphical code is 2D, doubling the code will make it only 1.4x (sqrt2) larger in each dimension, while the formula will double in lenght.
LabVIEW Champion . Do more with less code and in less time .
Similar Messages
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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.
ThanksDon'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 -
Hello All,
I am trying to open a file and write some data to a file within the formula node. A declaration like
file *in;
produces this error:
Formula Node:undefined variable.
Error on line 1 is marked by a '#' character: "file# *out;"
How does one do file I/O operations within the formula node?
Thanks,
KBHello KB,
it seems you are trying to write a LabView program by
inserting C-code into a formula node... That's not the way it should be.
As far as I know there is no way to open a file inside the formula node. (It's a "formula" node!) So you have to open the file with LabView for reading and/or writing. Use your prefered subVi from the file palette. Perhaps you have to convert the data to a format suitable for your formula node (like string to U8-array).
In my experience it's better to use Labview-code instead of the formula node. In my programs a formula node was always slower than Labview code. So you should think about converting the C-style code to Labview.
Best regards,
GerdW
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome -
How can I increment the index of an array in a formula node?
Hi,
I need some help with the formula node. I need an array, that increment every iteration of the code in the formula node. I need it to save amplitudes.
I thought i could do this with i++; i is the variable for my index.
Martin
Solved!
Go to Solution.Hello,
does it sound well to you ?
@+
Tinnitus
ps: sorry posts mixed
Message Edité par tinnitus le 12-15-2008 03:05 AM
CLAD / Labview 2011, Win Xp
Mission d'une semaine- à plusieurs mois laissez moi un MP...
RP et Midi-pyrénées .Km+++ si possibilité de télétravail
Kudos always accepted / Les petits clicks jaunes sont toujours appréciés
Don't forget to valid a good answer / pensez à valider une réponse correcte
Attachments:
inc_node.vi 6 KB -
Array output from formula node
How to get an array output from the formula node.I am trying to use a for loop inside the formula node and want an array output.
You cannot place a For or While Loop inside the formula node.
Here is what the Help Description says about the syntax inside the Formula Node:
Formula Node
Evaluates mathematical formulas and expressions similar to C on the block diagram. The following built-in functions are allowed in formulas: abs, acos, acosh, asin, asinh, atan, atan2, atanh, ceil, cos, cosh, cot, csc, exp, expm1, floor, getexp, getman, int, intrz, ln, lnp1, log, log2, max, min, mod, pow, rand, rem, sec, sign, sin, sinc, sinh, sizeOfDim, sqrt, tan, tanh. There are some differences between the parser in the Mathematics VIs and the Formula Node.
Place on the block diagram
Find on the Functions palette
Refer to Creating Formula Nodes and Formula Node Syntax for more information about the Formula Node and the Formula Node syntax.
Note The Formula Node accepts only the period (.) as a decimal separator. The node does not recognize localized decimal separators.
<SCRIPT type=text/javascript>if (typeof(writeVarRefs)=="function"){writeVarRefs("763");}</SCRIPT>
<SCRIPT type=text/javascript> if(typeof(lvrthelp763) != "undefined"){document.writeln(lvrthelp763)}</SCRIPT>
<SCRIPT type=text/javascript> if(typeof(lvfpga763) != "undefined"){document.writeln(lvfpga763)}</SCRIPT>
<SCRIPT type=text/javascript> if(typeof(lvemb763) != "undefined"){document.writeln(lvemb763)}</SCRIPT>
<SCRIPT type=text/javascript> if(typeof(lvpdahelp763) != "undefined"){document.writeln(lvpdahelp763)}</SCRIPT>
<SCRIPT type=text/javascript> if(typeof(lvtpchelp763) != "undefined"){document.writeln(lvtpchelp763)}</SCRIPT>
<SCRIPT type=text/javascript> if(typeof(lvblackfin763) != "undefined"){document.writeln(lvblackfin763)}</SCRIPT>
<SCRIPT type=text/javascript> if(typeof(lvdsp763) != "undefined"){document.writeln(lvdsp763)}</SCRIPT>
Example
Refer to the Create Function with Formula Node VI in the labview\examples\general\structs.llb for an example of using the Formula Node. -
I would like to cut and past in a list of comma seperated numbers and initialize an array of float32. Something like this would work in C.
float32 data[5] = {0,1,2,3,4};
Labview does not like this syntax when using a formula node. I have to do the following instead
float32 data[5];
data[0] = 0;
data[1] = 1;
What is the correct syntax for initializing arrays in lavview using a formula node. I would be amazed if Labview does not have this basic functionality.
thanks in advance
jim boblabview_noob wrote:
ttt, no one?
Probably because we are using LabVIEW to get away from text based code.
(I don't know if there is a syntax for the formula node, it's been too long. )
If you have LabVIEW 8.0 or higher, you can use matlab like sytax in a mathscript node. Of course you could just paste your list into a string constant and get the values with "spreadsheet string to array".
Message Edited by altenbach on 07-25-2007 12:24 AM
LabVIEW Champion . Do more with less code and in less time .
Attachments:
ArrayFormula.png 13 KB -
I want to take the Y value (being the amplitute) from the input signal and put it into a formula node. I keep getting the error signal as in the attached VI. Is there a way of seperating the value in labview?
Attachments:
Formula signal.vi 32 KBHi Cork,
yes, it's possible! And WTH: you can do it without a formula node with ready-to-use functions!
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome -
How do I get an array output on a Formula Node?
My problem is simply that I cannot figure out how to get an output on a Formula Node to be an array. Documentation states that "you must declare local arrays and output arrays in the Formula Node" but doesn't say anything more than than. Attempts to put something like "float32 out[100];" for an array output called "out" fail.
If anybody knows how you can do this or even knows if it is possible I would appriciate your help.
Thanks,
NaveenI found a typo in the formula node I was doing that was making the output not be an array. I don't think I was getting the error before but I was going to put together an example VI to attach here and I found it. So, thanks for your help even tho it was a stupid little mistake on my part.
-
String array into formula node
Hello,
I am taking data from SQL, I am getting multiple rows of data for many different devices. I would like to wire the data into a formula node so I can sepearate and sort via script. However, I am getting an error for "Polymorphic terminal cannot accept this data type". Is there a work around? Can I not wire in a string array to a formula node.
/r
TravoThere are lots of basic string VIs that you can use to parse the string and separate out the individual fields. I would recommend "programming" your application using script nodes. Use the native language. LabVIEW is a fully functional and capable programming language.
Mark Yedinak
"Does anyone know where the love of God goes when the waves turn the minutes to hours?"
Wreck of the Edmund Fitzgerald - Gordon Lightfoot -
How do I determine array size in a formula node
I am feeding an array into a formula node to perform an operation on. However the size of the array can be an arbitrary size. How can I determine its size to use for iterating through a for loop?
I suppose that I could add another input that is fed with the array size from the array palate but I would like to know if it can be done inside the formula node itself.Your own advice is the only and best one.
greetings from the Netherlands -
Hey there
I have a problem with my formula Node. I want to recieve a pictue from my camera and generate a 2d-array of the greyscalevalues. That works so far. Now i recieve an array with values between 0 and 4096 (because I have a 12-Bit picture).
Now the problem i have is, that the camera can dim the values, which are bigger than 2048. I tried to fix that problem with a Formula Node. But now i have the problem, that i can't connect the formula node to the intensity graph anymore.
I use the Labview Version 2013 and the camera is connectet with an ethernet-wire.
Can somebody please show me, how i can generate a 2d-array after the formula node?
Thanks
Attachments:
Formula Node.vi 282 KBHey muks
Yes, i take the picture from the camera and convert it to a 2d-array with the "ImageToArray" block.
Attachments:
ImageToArray.png 13 KB -
Arrays into the fromula node?
Hello,
I am trying to convert my voltages into pressures via the formula node but I am having trouble.
The situation is follows, I have a 1D array of single and I want to convert them using the formula node.
When I enter the equation into the node it tells me that there is an error on line 1 left brace needed.
What is the left brace, this must sound silly but I have no idea what to do.
Please help.
I have other formula nodes working fine but the inputs into them are not arrays they are just single elements (the mean of 1000 points for example).
Thanks
lp19In order to output an array from a formula node, you must declare the array variable.
float32 Y[100]; /* Declare 100-element array output
Inside the formula node, you must work with the arrays just like in C. The left brace is this -> [. It is looking for something like Y[0] = 1 + X[0]; where X is an array input. To make things simple you may consider placing your Formula node as it stands right now into a FOR loop. Your 1D array input will auto-index and your output will become an array as it tunnels out of the loop.
Daniel L. Press
PrimeTest Corp.
www.primetest.com -
HELP: Run-time array dimension in LabVIEW formula node
I need to dimension an array at run time within a formula node as follows:
int32 i,N;
N = sizeOfDim(inputArray,0);
float64 outputArray[N];
for (i = 0; i outputArray[i] = myfunction(inputArray[i]);
However, LabVIEW complains "Formula Node: index list expected". On the
other hand, if I say
float64 outputArray[1000];
LabVIEW is perfectly happy. But that's not what I need to do! Is there
an alternative
way of accomplishing my goal?
BTW, I've tried calculating N outside the formula node and then
presenting it as
an input with the same results. I've got a bad feeling that run time
array dimensioning
just isn't allowed.
TIA,
HughCan't you just use the Initialize Array function outside the formula node and pass that instead?
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In formula node how to use array outputs
someone has talked about this. but it is still a problem to me.
no matter how i declare the variable, the output terminal keeps a scalar.You should be able to declare it using:
int32 VarName[x][y];
That should make an array of 32bit integers.
See one of my earlier posts here: http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=135&HOID=506500000008000000EE2C0000&UCATEGORY_0=_49_%24_6_&UCATEGORY_S=0&USEARCHCONTEXT_TIER_0=0&USEARCHCONTEXT_TIER_S=0&USEARCHCONTEXT_QUESTION_0=array+formula+node&USEARCHCONTEXT_QUESTION_S=0
Try copying the code that I posted into your formula node and see if you get an array out. Or try the example I attached with the same code in it.
Let us know if you are still having trouble.
Brian
Attachments:
ArrayFormulaNode.vi 23 KB -
Can I create array inside formula node
I need to create and use array (multidimensional) inside a formula node. My LabVIEW version is 5.1.The input and output from/to formula node do not necessarily being array. Thank you.
You need to declare a variable to be an array. To declare a multidimensional array of 32 bit intergers enter this:
int32 VarName[x][y];
Where x=1st dimension size (rows) and y=2nd dimension size (columns). You can then operate on this like you would an array in a text based language. Try the entering the example below in a formula node.
int32 i;
int32 y[5][2];
for (i=0;i<5;i++)
y[i][1] = x[i]+1;
Where y is an output and x is an 1D array input.
Hope this helps...
Brian
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