For loop in formula node

Hi,
I wanna do some signal processing after I got the magnitude and phase infos from FFT. But the errors say that there is undefined variables. I am just wondering that here absP and angleP are both vectors. Can I express them like what I did in the attached vi? 3x.
Huihui
Attachments:
Untitled 12.vi ‏9 KB

Hi huihui,
do you just want to know the real and imaginary values of your signal?
Why use formula node at all?
Best regards,
GerdW
CLAD, using 2009SP1 + LV2011SP1 + LV2014SP1 on WinXP+Win7+cRIO
Kudos are welcome
Attachments:
Untitled 12.vi ‏13 KB

Similar Messages

Run for loop inside event node

Hi all,
We want to run for loop inside event node with 50ms delay. But when i am doing it the Labview is crashing. Please let me know if somebody did this.
Thanks in advance,
Regards,
Harish. G
Thanks & Regards,
Harish. G.

harishg92 wrote:
Hi all,
We want to run for loop inside event node with 50ms delay. But when i am doing it the Labview is crashing. Please let me know if somebody did this.
Thanks in advance,
Regards,
Harish. G
You're implementing a For loop inside an event structure? (I don't know of any event "node" in which you can run a For loop)
If so, that's a bad idea because LabVIEW won't be able to process any events while waiting for your For loop to get done, which might be why its crashing.
There are tricks to accomplishing what you're trying to do without putting any for loops inside event structure. See what I have attached and if it helps. "N" is number of times you run your For loop, timeout is whatever delay you want in each loop. This can be done in many ways without adding delays in events, another way could be to fire a separate subVI using Asynchronous call (without waiting for the VI to finish) during those delays, just make sure that such subVI finishes processing within your allocated time (that's how I'd ideally implement things). That method is better because you're doing minimal work inside events structure while using wait period wisely in a separate/parallel process.
I hope that I understood you correctly and did not go off on a tangent.
-BTC
New Controls & Indicators made using vector graphics & animations? Click below for Pebbles UI
Attachments:
ForLoop inside Event Structure.vi ‏11 KB

Dead loop in formula node

Hi,
I have encountered the following problem in a formula node. Everything seems simple and right. But there is no output and the loop goes on forever. The sizes of both input arrays are the same. Need your advice. Thanks.
Rut
Attachments:
Algorithm.vi ‏11 KB

Look, I am far out on a limb here, because I am not a C programmer. Whatever you're doing would make more sense from a FORTRAN point of view.
The LabVIEW formula node uses BNF notation (check the help), which is in many ways C like. So the syntax for a FOR loop is:
for ( InitExpression ; CondExpression ; LoopExpression ) Statement
This means the loop iterates until "CondExpression" is true.
Do a google search on "C For loop" and you might find for example pages like:
http://www.hitmill.com/programming/cpp/forLoop.htm
http://www.geocities.com/learnprogramming123/Clesson8Beginner.htm
Your condExpression is "n1-1", which, during the execution of the node is a constant. For example if you array size is 50, n1-1=49, FOREVER! The condition is never true so the loop will never stop.
I hope somebody more knowledgable will chip in at one point.
LabVIEW Champion . Do more with less code and in less time .

How to change content in the formula node of the current vi

Actually I want to give formula with array index.
My formula p=a[0]-30; But i couldnot give array index in the formula expression..
Please help me in this issue.

Muthu92 wrote:
Thank you for your reply. It is very useful for me. But i can't give conditional operator in that operator. It is showing error.
My Test cases
A[0]+A[1]>150
A[31]-50 <100.
If those are your exact statements, then they don't make sense in a formula node. You have to use them in an if-statement or some other type of control logic. This mimics text-based programming languages such as C... See here for instructions on formula node syntax: http://zone.ni.com/reference/en-XX/help/371361G-01/lvhowto/formula_node_syntax/
For instance, you COULD say something like:
**In this example, let A[0] == x, A[1] == y, A[31] == z**
if(x+y>150)
/* do something if this is true */
else if(z-50 < 100)
/* do something else */
EDIT:
It should also be noted that Variable Names MUST be lowercase!! I just discovered this
EDIT2:
I stand corrected. After trying to create an example and digging through the LabVIEW Help, I stumbled across this:
Differences between the Parser in the Mathematics VIs and the Formula Node
The parser in the Mathematics VIs supports all elements that Formula Nodes support with the following exceptions:
Variables—Only a, a0, ..., a9, ... z, z0, ..., z9, are valid.
Logical, conditional, inequality, equality—?:,, &&, !=, ==, <, >, <=, and >= are not valid.
Functions—atan2, max, min, mod, pow, rem, and sizeOfDim are not valid. You can use these functions in a Formula Node or use their corresponding LabVIEW functions.
So it DOES NOT seem like Eval Formula Node can do conditionals like you want. I would just implement them using a LabVIEW based algorithm after all. Trying to out smart the formula nodes to avoid simple LabVIEW code is just too much of a hassle
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If someone helped you out, please select their post as the solution and/or give them Kudos!

Eval formula node expressions

Hi
What are the acceptable formula inputs for the Eval Formula Node VI?
The help files do not mention much. It took me a long time to work out that 2*pi needed to be written pi(2).
I would also like to know if I can perform 'if' statements and what the correct syntax is.
My application uses two inputs (an integer and a voltage reading), a formula that the user enters (eval formula node vi), and an output number (DBL).
UniSA, Mawson Lakes, South Australia - LV 8.6.1
Attachments:
FormulaNodeExampleLV8_6.vi ‏12 KB

Hi mikie121
Take a look here. The syntax, operators, and functions links will be what you are looking for.
Joe Daily
National Instruments
Applications Engineer
may the G be with you ....

How do I use For loop to check each node and import them to a new document?

In my function I would like to use a For loop to get all the statutes (xml) inside the object
objXmlBcaResponseDoc. In my case there are 2 statutes. I would like the output to look like the one I have posted here below. I am not sure how to do the For loop. The commented For loop is from another function but it is not working inside
this function.
The output is added into the **objXmlResponseMessageDoc** object and should look like this with 2 statutes (ns1:Statute) and a totalCount=2
<BasicSearchQueryResponse xmlns="http://crimnet.state.mn.us/mnjustice/statute/service/4.0">
<StatutesXml>
<Statutes runType="Request" runDateTime="2015-03-17T10:23:04" totalCount="2">
<ns1:Statute xmlns:ns1="http://crimnet.state.mn.us/mnjustice/statute/messages/4.0">
<StatuteId xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">8471</StatuteId>
<Chapter xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">60</Chapter>
<Section xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">55</Section>
<Subdivision xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0"/>
</ns1:Statute>
<ns1:Statute>
<StatuteId xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">9722</StatuteId>
<Chapter xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">90</Chapter>
<Section xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">25</Section>
<Subdivision xsi:nil="true" xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0"/>
</ns1:Statute>
</Statutes>
</StatutesXml>
</BasicSearchQueryResponse>
My xml doc is found inside objXmlBcaResponseDoc Here is xml inside
objXmlBcaResponseDoc object
<BasicSearchQueryResponse xmlns="http://crimnet.state.mn.us/mnjustice/statute/service/4.0">
<ns1:Statutes xmlns:ns1="http://crimnet.state.mn.us/mnjustice/statute/messages/4.0">
<ns1:Statute>
<StatuteId xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">8471</StatuteId>
<Chapter xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">60</Chapter>
<Section xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">55</Section>
<Subdivision xsi:nil="true" xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0"/>
</ns1:Statute>
<ns1:Statute>
<StatuteId xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">9722</StatuteId>
<Chapter xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">90</Chapter>
<Section xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0">25</Section>
<Subdivision xsi:nil="true" xmlns="http://crimnet.state.mn.us/mnjustice/statute/4.0"/>
</ns1:Statute>
</BasicSearchQueryResponse>
Here is my function
Function GetStatutesByChapter(ByVal aobjXmlGetStatuteRequestNode As XmlNode, ByVal aobjXMLNameSpaceManager As XmlNamespaceManager, ByVal aobjBroker As ServiceCatalog.Library.v4.Broker) As XmlDocument
Dim objXmlRequestMessageDoc As XmlDocument
Dim objXmlResponseMessageDoc As XmlDocument
Dim intCount As Integer
aobjBroker.PostMessageWarehouseInformationalMessage("Chapter found.", 1)
objXmlResponseMessageDoc = New XmlDocument
'Add the first element into the document GetStatuteByChapter with its namespace
objXmlResponseMessageDoc.AppendChild(objXmlResponseMessageDoc.CreateElement("BasicSearchQueryResponse", "http://crimnet.state.mn.us/mnjustice/statute/service/4.0"))
'Build the initial response document
objXmlResponseMessageDoc = New XmlDocument
'Add the first element into the document GetStatutesResponse with its namespace
objXmlResponseMessageDoc.AppendChild(objXmlResponseMessageDoc.CreateElement("GetStatutesResponse", "http://www.courts.state.mn.us/StatuteService/1.0"))
'Add a child node to the GetStatutesResponse node
objXmlResponseMessageDoc.SelectSingleNode("ss:GetStatutesResponse", aobjXMLNameSpaceManager).AppendChild(objXmlResponseMessageDoc.CreateElement("StatutesXml", "http://www.courts.state.mn.us/StatuteService/1.0"))
objXmlResponseMessageDoc.SelectSingleNode("ss:GetStatutesResponse/ss:StatutesXml", aobjXMLNameSpaceManager).AppendChild(objXmlResponseMessageDoc.CreateElement("Statutes", "http://www.courts.state.mn.us/StatuteService/1.0"))
'Convert the node Statutes into an element and set the runType attribute (runType="Request") by adding it's value Request
CType(objXmlResponseMessageDoc.SelectSingleNode("ss:GetStatutesResponse/ss:StatutesXml/ss:Statutes", aobjXMLNameSpaceManager), System.Xml.XmlElement).SetAttribute("runType", "Request")
'Convert the node Statutes into an element and set the attribute (runDateTime="2015-03-05T10:29:40") by adding it
CType(objXmlResponseMessageDoc.SelectSingleNode("ss:GetStatutesResponse/ss:StatutesXml/ss:Statutes", aobjXMLNameSpaceManager), System.Xml.XmlElement).SetAttribute("runDateTime", Format(Now, "yyyy-MM-ddTHH:mm:ss"))
'Create the BCA request message
objXmlRequestMessageDoc = New XmlDocument
objXmlRequestMessageDoc.AppendChild(objXmlRequestMessageDoc.CreateElement("ns:BasicSearchQueryRequest", aobjXMLNameSpaceManager.LookupNamespace("ns")))
objXmlRequestMessageDoc.SelectSingleNode("ns:BasicSearchQueryRequest", aobjXMLNameSpaceManager).AppendChild(objXmlRequestMessageDoc.CreateElement("ns1:BasicSearchCriteria", aobjXMLNameSpaceManager.LookupNamespace("ns1")))
objXmlRequestMessageDoc.SelectSingleNode("ns:BasicSearchQueryRequest/ns1:BasicSearchCriteria", aobjXMLNameSpaceManager).AppendChild(objXmlRequestMessageDoc.CreateElement("ns2:Chapter", aobjXMLNameSpaceManager.LookupNamespace("st")))
objXmlRequestMessageDoc.SelectSingleNode("ns:BasicSearchQueryRequest/ns1:BasicSearchCriteria", aobjXMLNameSpaceManager).AppendChild(objXmlRequestMessageDoc.CreateElement("ns2:Section", aobjXMLNameSpaceManager.LookupNamespace("st")))
objXmlRequestMessageDoc.SelectSingleNode("ns:BasicSearchQueryRequest/ns1:BasicSearchCriteria", aobjXMLNameSpaceManager).AppendChild(objXmlRequestMessageDoc.CreateElement("ns2:Subdivision", aobjXMLNameSpaceManager.LookupNamespace("st")))
'Uncomment last working section below
objXmlRequestMessageDoc.DocumentElement.SelectSingleNode("ns1:BasicSearchCriteria/st:Chapter", aobjXMLNameSpaceManager).InnerText = aobjXmlGetStatuteRequestNode.SelectSingleNode("ss:Statute/ss:Chapter", aobjXMLNameSpaceManager).InnerText
'check if there is a section and or subdivision if it is there then set the value
If Not (aobjXmlGetStatuteRequestNode.SelectSingleNode("ss:Statute/ss:Section", aobjXMLNameSpaceManager) Is Nothing) Then
objXmlRequestMessageDoc.DocumentElement.SelectSingleNode("ns1:BasicSearchCriteria/st:Section", aobjXMLNameSpaceManager).InnerText = aobjXmlGetStatuteRequestNode.SelectSingleNode("ss:Statute/ss:Section", aobjXMLNameSpaceManager).InnerText
End If
If Not (aobjXmlGetStatuteRequestNode.SelectSingleNode("ss:Statute/ss:Subdivision", aobjXMLNameSpaceManager) Is Nothing) Then
objXmlRequestMessageDoc.DocumentElement.SelectSingleNode("ns1:BasicSearchCriteria/st:Subdivision", aobjXMLNameSpaceManager).InnerText = aobjXmlGetStatuteRequestNode.SelectSingleNode("ss:Statute/ss:Subdivision", aobjXMLNameSpaceManager).InnerText
End If
'check if there is a section and or subdivision if it is there then set the value
aobjBroker.PostMessageWarehouseSnapshot(objXmlRequestMessageDoc.OuterXml, "Request Message", 1)
'Call the BCA service
intCount = 0
'This is where I want to use a For loop to check for the statutes found using the Chapter
'Loop through each Id
'For Each objXmlStatuteIdNode In aobjXmlGetStatuteRequestNode.SelectNodes("ss:Statute/ss:StatuteId/ss:Id[string-length(.)>0]", aobjXMLNameSpaceManager)
'Create the BCA request message
'objXmlRequestMessageDoc = New XmlDocument
'objXmlRequestMessageDoc.AppendChild(objXmlRequestMessageDoc.CreateElement("ns:SingleStatuteRequest", aobjXMLNameSpaceManager.LookupNamespace("ns")))
'objXmlRequestMessageDoc.SelectSingleNode("ns:SingleStatuteRequest", aobjXMLNameSpaceManager).AppendChild(objXmlRequestMessageDoc.CreateElement("ns:statuteId", aobjXMLNameSpaceManager.LookupNamespace("ns")))
'objXmlRequestMessageDoc.DocumentElement.SelectSingleNode("ns:statuteId", aobjXMLNameSpaceManager).InnerText = objXmlStatuteIdNode.InnerText aobjBroker.PostMessageWarehouseSnapshot(objXmlRequestMessageDoc.OuterXml, "Request Message", 1)
'intCount = intCount + 1
'objXmlBcaResponseDoc = New XmlDocument
'File name is BCASearchQueryResponse.xml
'objXmlBcaResponseDoc.Load("\\j00000swebint\mscapps\deve\appfiles\temp\BCASearchQueryResponse.xml")
'objXmlResponseMessageDoc.DocumentElement.SelectSingleNode("ss:StatutesXml/ss:Statutes", aobjXMLNameSpaceManager).AppendChild(objXmlResponseMessageDoc.ImportNode(objXmlBcaResponseDoc.DocumentElement.SelectSingleNode("ns1:Statute", aobjXMLNameSpaceManager), True))
'Next
'Count how many Statute nodes found
CType(objXmlResponseMessageDoc.SelectSingleNode("ss:BasicSearchQueryResponse/ss:StatutesXml/ss:Statutes", aobjXMLNameSpaceManager), System.Xml.XmlElement).SetAttribute("totalCount", CStr(intCount))
Return objXmlResponseMessageDoc
End Function

What is XPath and what does it do that you're impressed with?
Yes, I see your link, but give me the abbreviated elevator speech on what it is please. It has me curious.
http://searchsoa.techtarget.com/definition/XPath
http://www.techrepublic.com/article/easily-navigate-xml-with-vbnet-and-xpath/
http://www.techrepublic.com/article/using-xpath-string-functions-in-xslt-templates/
The way that all this is being used by me now on a project is the HTML controls on the screen are built by XML not only about what the controls are and their attributes, but the data from from the database is XML too with both going through transfermations
vis XSLT as the HTML controls are built dynamically by XML data for the controls and the XML database data with decision being made in the transfermation on the fly.
There are many usages with Xpath not just this one I am talking about with Xpath. You can do the same kind of thing with XAML and WPF forms as they are dynamically built. But it goes well beyond what I am talking about and the usage of Xpath. Xpath 3.0
is the latest version.
http://www.balisage.net/Proceedings/vol10/html/Novatchev01/BalisageVol10-Novatchev01.html
Thanks - I'll look into that at some point.
Still lost in code, just at a little higher level.

Node removing in a Tree, for loop, and Enumeration

Hi there
it should be pretty easy, however i'm stuck with this code:
public void supprNode(DefaultMutableTreeNode node){
for(en = node.preorderEnumeration();e.hasMoreElements();){
DefaultMutableTreeNode tmpNode= (DefaultMutableTreeNode) en.nexElement();
if (tmpNode instanceof myderivedNodeClass)
tmpNode.doSomething();
if(!tmpNode.isRoot())
removeNodeFromParent(tmpNode);
}The problem is, the for loop doesn't traverse all the elements. That's if i call removeNodeFromParent. Is the enumeration updated twice?
ie if my tree is
root
-1
-2
-3after the call of supprNode(root) i get:
root
-2And i really don't understand why.

Hi!
If you look at the apidoc of DefaultMutableTreeNode.preorderEnumeration() you will see following text:
* Modifying the tree by inserting, removing, or moving a node invalidates
* any enumerations created before the modification.
So you should copy the elements of the enumeration in a separate list and iterate then over this list!
With kind regard,
Mathias

Repeating nodes using FOR loop but when concating XML string then concating only last iteration of FOr loop ??

I stuck with a problem that I am using FOR loop for generating repeating nodes.
Now when I concat the generated node in the main node then I got only last iteration of that FOR loop.
can anybody suggest me a way to handle this error....
FOR i IN 1..pl_phone_tab.Count
LOOP
SELECT xmlelement("Phone"
                                    ,xmlelement("PHONETYPE",xmlattributes('01' AS "dmnADRP_PHONETYPE"),pl_phone_tab(i).p_phtype_tab)
                     ,xmlelement("PHONENUM",pl_phone_tab(i).p_phnum_tab)
                     ,xmlelement("PRIMARY_CONTACT",pl_phone_tab(i).p_prcon_tab)
INTO p_phone_xml
FROM dual; END LOOP;
SELECT xmlelement("PhoneInfo"
                       ,xmlconcat(p_phone_xml))
INTO p_phone_info_xml
FROM dual;
here I am getting only one node but there has to be two nodes for PHONE node

Not that I'm encouraging you but here are two standalone examples explaining how to do what you want :
1) Loop through the input collection and append each node to its target container :
SQL> declare
2
3    type t_emp_tab is table of scott.emp%rowtype;
4
5    emp_tab       t_emp_tab;
6    emp_info_xml xmltype;
7    emp_xml       xmltype;
8
9 begin
10
11    -- filling emp_tab with data
12    select e.*
13    bulk collect into emp_tab
14    from scott.emp e
15    where e.deptno = 10;
16
17    emp_info_xml := xmltype('<EmpInfo/>');
18
19    -- looping through emp collection and appending to EmpInfo element
20    for i in 1 .. emp_tab.count loop
21      select appendchildxml(
22               emp_info_xml
23             , '/*'
24             , xmlelement("Emp"
25               , xmlattributes(emp_tab(i).empno as "id")
26               , xmlforest(
27                   emp_tab(i).ename as "Name"
28                 , emp_tab(i).job as "Job"
29                 )
30               )
31             )
32      into emp_info_xml
33      from dual;
34    end loop;
35
36    dbms_output.put_line(emp_info_xml.getclobval(1,2));
37
38 end;
39 /
<EmpInfo>
<Emp id="7782">
    <Name>CLARK</Name>
    <Job>MANAGER</Job>
</Emp>
<Emp id="7839">
    <Name>KING</Name>
    <Job>PRESIDENT</Job>
</Emp>
<Emp id="7934">
    <Name>MILLER</Name>
    <Job>CLERK</Job>
</Emp>
</EmpInfo>
PL/SQL procedure successfully completed
2) Build a secondary collection of XML nodes and use XMLAgg to aggregate them in one go :
SQL> declare
2
3    type t_emp_tab is table of scott.emp%rowtype;
4
5    emp_tab       t_emp_tab;
6    emp_info_xml xmltype;
7    emp_xml_tab   xmlsequencetype := xmlsequencetype();
8
9 begin
10
11    -- filling emp_tab with data
12    select e.*
13    bulk collect into emp_tab
14    from scott.emp e
15    where e.deptno = 10;
16
17    -- looping through emp collection and appending to the collection of Emp nodes
18    for i in 1 .. emp_tab.count loop
19
20      emp_xml_tab.extend;
21
22      select xmlelement("Emp"
23             , xmlattributes(emp_tab(i).empno as "id")
24             , xmlforest(
25                 emp_tab(i).ename as "Name"
26               , emp_tab(i).job as "Job"
27               )
28             )
29      into emp_xml_tab(i)
30      from dual;
31
32    end loop;
33
34    select xmlelement("EmpInfo", xmlagg(t.column_value))
35    into emp_info_xml
36    from table(emp_xml_tab) t ;
37
38    dbms_output.put_line(emp_info_xml.getclobval(1,2));
39
40 end;
41 /
<EmpInfo>
<Emp id="7782">
    <Name>CLARK</Name>
    <Job>MANAGER</Job>
</Emp>
<Emp id="7839">
    <Name>KING</Name>
    <Job>PRESIDENT</Job>
</Emp>
<Emp id="7934">
    <Name>MILLER</Name>
    <Job>CLERK</Job>
</Emp>
</EmpInfo>
PL/SQL procedure successfully completed
Both solutions give the same output.
Test them both and see which one fits better into your scenario.

Is it possible to put property node inside for loop?

I have created three separate property nodes (plot color) for my 3 XY graphs.
Is it possible to have one property node, say plot_color_i and put this inside the for loop where i runs from 1 to N,
where plot_color_1 would update XY Graph 1, plot_color_2 would update XY Graph 2, etc.?
See the attached VI.
Solved!
Go to Solution.
Attachments:
XY Plot Example.vi ‏18 KB

Yes. Create an array of references of the XY graphs and have that auto-index into the property node in the For Loop
Attachments:
XYPlotExampleMOD.vi ‏18 KB

Formula node for array

hi
i want to convert the values of an array using a different formula for each value in the array. Can i use formula node for this? if yes how
if no then is there any other method except for extracting each one individually and converting?

kunal227 wrote:
there are 16 elements in the array and the number remains constant (actually they are temp values acquired by a fieldpoint hardware).
the formula is a linear conversion (for example y = m*x + C) corresponding to the calibration curve of individual thermocouple connected to the fieldpoint hardware. every thermocouple has a different calibration curve and hence every element in the array is converted using a different linear formula.
All you need is an array of [m] and an array of [C], all the same size as your data arrray. No formula node needed.
(I think that's what mikeporter had in mind above)
Message Edited by altenbach on 07-24-2007 03:38 PM
LabVIEW Champion . Do more with less code and in less time .
Attachments:
CorrectedArray.png ‏4 KB

Combining formula node and arrays for calculation

Hello all!
I have two arrays containing values defined by me. Each value of respective column and row index shall be used in a formula to calculate the new value for the respective column and row, to build a new array for further use. This shall be done several times during a simulation with variable function parameters.
I am aware that I should probably use a for loop for this calculation, but I am curious to how I should build such a procedure.
Any ideas?

Hi Euler123,
Let's say that you have an array of fix size and with values in it. Then you'll need to use auto indexing at the beginning of each for loop input tunnel (usually it is by default for for loops) as shown below:
In the first iteration of the other for loop, it will take the first row values [1, 2, 3] and pass it to the inner for loop (unless you want to extract the values for each column, transpose that 2D array before connecting it to the outer for loop). In the inner for loop, it will execute 3 times and each iteration it will extract each element from the array obtained from the outer for loop.
To build the new array, it's just the opposite. Pass the element out from the for loop and instead of getting a last value tunnel, you'll get an auto indexing tunnel (default for for loops).
Anyways, you'll need to get some basic understanding on LabVIEW first. Here's some tutorials to aid you on understanding For Loops.
http://www.youtube.com/watch?v=ziOnPNJgeVg
Here's some additional notes which might help you:
http://zone.ni.com/reference/en-XX/help/371361J-01/lvhowto/auto_indexing_1/
http://zone.ni.com/reference/en-XX/help/371361H-01/lvhowto/auto_indexing_1/
http://zone.ni.com/reference/en-XX/help/371361G-01/lvhowto/auto_indexing_1/
Play around with For Loops and use something to slow the execution down like Highlight Execution which allows you to see what is going on. Else, take up some LabVIEW courses
Warmest regards,
Lennard.C
Learning new things everyday...

Using the Formula Node for PDA

I get a compile error when I use C code inside the formula node. Is it possible to use C Code inside the formula node for PDA applications? Do I have to include any file while building the executable for the PDA

Ok, I was able to successfully build an executable file without error. I attached the screen shots of your program in execution. Does this look like the desired result?
I'm confused as to why I can build and run the program on my machine. I have LabVIEW 7.0 and Windows XP. What version of Windows and LabVIEW are you using? Also, are you getting the error window when you try to build an executable or when you attempt to run the VIs within LabVIEW?
Regards,
-Joe-
Attachments:
tutor.JPG ‏100 KB
tutor2.JPG ‏122 KB
detector.JPG ‏46 KB

Cannot Access Shortcut Menu for Adding Input/Output in Formula Node

This is a wierd problem. I cannot access the shortcut menu in formula node. I right click the border, nothing happens. Anyone run into this before? Is there any other way to add inputs and outputs?
I am running Vision Builder AI and want to use a formula node in my calculator tool.
Solved!
Go to Solution.

As the saying goes, "when you hear hoofbeats, think horses and not zebras". Let's get a few things out of the way.
Is the VI in edit mode?
Is autotool on?
Drop a fresh FN on a New VI and try it again.
The only other way I know to add/remove inputs is scripting, let's not go there.
I have had a few issues with context menus, very few which persisted past a LV and/or computer restart, so I won't rule out a zebra just yet.

If-then statement in formula node

**Note - The attached file shows the current block diagram.
I have a formula node inside a for loop. Inside the formula node I am trying to program the if-then statement:
If T1<2.0E-5 OR T1>5.5E-4 THEN GOTO 3
U7=U7+V
I have 4 items I need help with:
(1) Is 'II' the correct operator for 'OR'?
(2) Is 'goto' an acceptable operator within LabVIEW?
(3) 'U7' is building a 1D array. How do I need to define it? Is it simply 'int U7'? Also, I will add an output value named 'U7' on the formula node wall with an indicator wired to it from outside the for loop.
(4) Is my use of the equal sign appropriate or do I need to use '=='?
Thanks for the help.
Philip
Attachments:
if-then_in_FN.jpg ‏18 KB

Thanks for the help. I went ahead and rewrote the program so I could omit the 'goto's. Another problem that I am having is that I want 2 statements for 1 assignment:
if (T1>=.002004 && T1<=.002584)
B1=U
A1=V;
I want to assign both B1 and A1 values when the above condition is true. I tried a comma between the U and A1 but it doesn't work as well. Should I define A1 and B1 separately? Or would this create problems?
if (T1>=.002004 && T1<=.002584)
B1=U;
if (T1>=.002004 && T1<=.002584)
A1=V;
Thanks,
Philip

"Eval Parsed Formula Node VI" does not return outputs in predefined order

I make a data analysis program, where the data consists of some million events and each event has e.g. 4 channels and 1-5 hits on each channel.
I would like the user to select different expressions of these channels to give coordinates to plot in a 2D histogram (increment a bin in Intensity Graph), e.g. for some experiment you want to show x=ch1-ch2; y=ch1+ch2+ch3+ch4; while in another experiment you want x=ch1-123; y=123-ch2;
There are other VIs that use static LabView-code for the normal things, but now after a few years of adding to this program I find that it would be quite good with a general plotter and let the user specify simple expressions like this. Also with the "normal" static plots, there is a need to filter out bad data and then it would be much simpler both to program and use if you could write text expressions with boolean logic to combine multiple filters. Making a LabView code and GUI that allows AND/OR/parenthesis combinations of expressions will be quite an effort and not very reusable.
So, with the above motivation, I hope you see that it would make sense to have a useable string formula evaluator in LabView. I find some info about MathScript's user-defineable functions, but haven't managed to get MathScript working in LV2010 yet (maybe some licensing or installation issues, I think I had it in 8.6). But I think it would be possible to do most of what I want for the display-part (not the filtering) with the simpler Eval/Parse Formula Node VIs and suitable use of the limited variable name space. So I started testing, and found a quite annoying issue with how the evaulator works.
To the parser, you are expected to send an array of output variable names. But then it ignores this array, and returns one output per assignment/semicolon in the formula, in the order of the formula text. Since the static parts of my program need to know what the output values mean (which of them is x and which is y), I would have to rely on the user not using any intermediate variable and defining x before y. The attached screenshot demonstrates the problem, and also that it has been solved by NI statff in the "Eval Formula Node VI" which does the appropriate array-searching to extract only the pre-defined outputs, in their expected order. But using that VI is about 100 times as slow, I need to pre-compile the formula and then only use the evaulator in the loop that runs over a million events.
I don't know if I'll take the time to make my own tweks to the parsing stage (e.g. preparation of array-mapping to not have to repeat the search or maybe hacking the output list generated by the parser) or if I'll have to make it in a static Formula Node in the block-diagram (which supports more functions), so that the user has to run with development environment and stop the program to change the plotting function. But I wanted to share this trouble with you, in hope of improvments in future LabView versions or ideas from other people on how I could accomplish my aim. I have MATLAB-formula node possibility too, but is far as I have seen the only place the user could update the formula would then be in a separate .m file, which is re-read only when typing "clear functions" in the Matlab console window. (Having this window is also an annoyance, and perhaps the performance of calling Matlab in every iteration is not great.)
Besides this issue, it also seems very strange there is virtually no support for conditional expressions or operators in Formula Node evaulated formulas (called Mathematics VIs in the documentation). Maybe using (1+sign(a-b))/2 you can build something that is 0 when a<b and 1 when a>b, but it is not user friendly! Would it really be diffcult to add a function like iif(condition, return_value_if_true, return_value_if_false) to replace the unsupported "condition ? if_true : if_false" operator? Would it really be difficult to add support for the < <= >= > == || && operators? Although compiled to an assemply language, this can't exactly be difficult for a CPU.
Attachments:
LV script test.png ‏62 KB
LV script test.vi ‏18 KB

(1) You can put any kind of code inside an event structure with the limitation that it should be able to complete quickly and without user interaction. For example a while loop for a newton-raphson method is fine, but an interactive while loop where the stop condition depends on user iteraction is not recommended. By default, event structures lock the front panel until the event completes, so you would not even be able to stop it.
(2) Yes, you can do all that. LabVIEW has no limitation as a programming language. Use shift registers to hold data and state information, the manipulate the contents as needed.
(3) I would recommend to use plain LabVIEW primitives instead of formula nodes. Show us your code so we can better see what it's all about. Obviously you have a mismatch betweeen scalars and arrays. It is impossible from the given information where the problem is.
(4) Yes, look inside the nonlinear curve fit VI (you can open it an inspect the code!). One of the subVIs does exactly that. Just supply your model VI.
LabVIEW Champion . Do more with less code and in less time .

For loop in formula node

Similar Messages

Maybe you are looking for