For Loop Structure

Hi... are multiple initializations inside the firt part of a for loop allowed in Java?
for (int i = 0, int j = 0; i < someArray.length; ++i, j = j + 2) {
//doin' somethin'
}

If you find yourself asking a question along the lines of is this possible in java, then why don't you just write some code, compile it and run it.
If you did that you would find that indeed it is legal.
If on the other hand you are asking for our opinion on this type of code, then you should phrase the question differently.
This is probably a sign of bad design... you could probably come up with a better way to do what you require...

Similar Messages

Is it possible to use a "for loop" structure to represent DAQ of 16 channels?

Hi,
I tried to search but I failed to find a similar problem so I am posting this problem here.
I have a temperature DAQ board which has 16 channels, and I am using all 16 channels to record and monitor temperature data.
When I writed blocks for all 16 channels, a mess was created (as you can see in my attached program). I have noticed that all the VIs for the 16 channels have similar structure, so I was thinking whether we can represent all 16 channels with a "for loop" strucutre with a pointer i scanning from i=1 to 16 as we usually do in Matlab or Fortran.
For instance, we may try to simplify the code like:
for i=1:1:16
acquire data from channel i
show data from channel i in X-Y graph
write data from channel i to excel in every 10 seconds
end
I could not do it myself because I cannot find a "pointer" to represent each channel.
Does anyone know how to do this in LabVIEW? Thank you.
It is said that it is best if we can put all of our code within the screen of a monitor we use by using subVIs to divide the code into many subroutines. But I found it quite difficult to do so as I have too many controls as inputs and indicators as outputs. Also, I use property node to read and write frequently, which make things harder....
Attached code does not work as it requires the 9213 hardware, and for simplicity I deleted irrelavent modules. But if you need I can upload one that may work by modifying the read VI.
Thank you.
Attachments:
ask for help.vi ‏132 KB

Yup, instead of all these 1D arrays, use a single 2D array. Your code could be reduce to <10% of the current size. I am sure it would fit easily on a single screen.
Also try to do some tutorial or take some courses. I realy don't think you are ready to tackle a system of this magnitude at this time.
Your code is just peppered with very poor choices. Some things you apparently haven't figured out:
index array is resizable. There is no need to create dozens of parallel instances, all wired to the same array and all with a unique index diagram constant. If you want all elements in order, the indices don't need to be wired at all.
Replace all your value property nodes with local variables. Much more efficient. Then redesign the code so you don't even need most of the local variables.
You can use built array to append elements to an existing array. Using "insert into array" is much more complicated an error prone.
It is not a good idea to have deeply stacked while loops with the innermost loop having long delays and indeterminate stop conditions. That just gums up the gears.
Learn about proper code architectures, state machines, etc.
Get rid of that gigantic, all encompassing stacked sequence. I am sure you can find a better way to reset three booleans when the code is about to stop. In fact it is typically more reasonable to set things to a defined state when the program starts to avoid problems due to accidental value changes at edit time.
Don't use hidden control/indicators as data storage and interloop communication via local variables. There are better ways.
You can wire the reminder or Q&R directly to a case structure. No need for e.g. "=0".
Don't use ambiguous labels, e.g.a boolean labeled "Dampers on or off". Nobody will be able to later figure out if TRUE corresponds to ON or OFF. Could it be that TRUE mean it is either ON or OFF and FALSE that it is in some imternediate position?
LabVIEW Champion . Do more with less code and in less time .

For loop indexing?

Is it possible to change indexing step in labView "For Loop" structure? By
default this value is 1, and I need to make a step value different from "1"
like in C example:
for (index=0; index < 100; index++) {}; // step=1
for (index=0; index < 100; index=index+3) {}; // step=3
Sergey Yakovlev, Berlin,
[email protected]

Hallo, Sergey,
Du (yakovlev) meintest am 21.09.01 zum Thema for loop indexing?:
> Is it possible to change indexing step in labView "For Loop"
> structure? By default this value is 1, and I need to make a step
> value different from "1" like in C example:
> for (index=0; index < 100; index++) {}; // step=1
> for (index=0; index < 100; index=index+3) {}; // step=3
What about
j:=i*3
and i is incremented by 1
Greetings!
Helmut
Please excuse my gerlish!

Using a For Loop Index for Array Element Number?

Hi. Thanks in advance for the help. I can't seem to find what I want to do here using the search function... probably because I don't know how to frame the question appropriately. Ignore the title to this post cause it's probably wrong vocabulary for what I want to do.
Here's the situation:
I have a 2D array where the first column is the X data and each subsequent column is Y data (call it Y1...Yn). The n-value varies from run to run (some runs have 4 columns of data, some have 20), but that is easily gathered when reading the data file. I need to perform a number of operations on each set of data, the least of which is smoothing the data and graphing it, so I'm limiting my discussion to these 2 operations.
What I want is a for loop structure where the indexing of the loop tracks the Y1...Yn columns, grabs each column for the iteration, performs the relevant analysis, and spits out the result, but in a stackable manner. Thus the title; I want to use the for loop's index to mark the array element for building a new array.
See the image attached. A 2D array of 9 columns (X, Y1...Y8) is analyzed such that each data set, (X, Y1), (X, Y2)...(X, Y8) is bundled, graphed, run through a B-spline Fit, of which is also graphed. I need to replace this with something that looks like the for loop structure shown.
I just don't know how to get those two data bundles [(X, Yi) and it's smoothed pair] out of the for loop in a stacked set from every iteration of the for loop.
Again the title, I think I want to build a new array where i use the index of the for loop to control the entries of the new array. But I can't see how to do that.
Any help would be appreciated.
Attachments:
NeedForLoopForThis.PNG ‏30 KB

Hello H.R. Dunham, and welcome to the forum!
It seems that you may be looking for Auto-Indexing, a basic feature of loops in LabVIEW. You'll need to transpose your array before wiring it into the for loop, as elements are auto-indexed by row before column, but at that point you should be able to operate on each column and output an array of n cluster elements corresponding to your input columns. Auto-indexing tunnels look like brackets to indicate each element will be indexed automatically- this should be the default when wiring an array into a for loop or when wiring anything out of a for loop.
As for how to build your pairs, I suggest removing the X column and creating a "starter" cluster containing your X data and placeholder Y data before entering your "Y" processing loop. Use the bundle by name function in the for loop to insert your processed column data into the cluster and auto-index the cluster output. Flow would be something like this:
1) Gather data
2) Split X and Y using standard array operations
3) Create "template" cluster with shared X data
4) Pass template cluster and Y-column array into an auto-indexed for loop.
5) Insert processed Y data into cluster inside loop.
6) Auto-index cluster data out of loop.
This tutorial is probably also a good place to get started:
Getting Started with NI LabVIEW Module 3: Loops
http://www.ni.com/white-paper/7528/en/
Hope that helps!
Regards,
Tom L.

I'm having problems manipulating array data within a for loop, and extracting the required sub-arrays generated.

Hi,
I'm using labVIEW V5.1
I'm trying to generate 10 1D arrays, the first array is initialized to all zeroes, then I have set up a for loop which shifts the first element by 1, then a random number is placed into the first element position. I am using a shift register to feed back in the newly generated array into the start of the loop.
By the end of the each loop I want to be able to use the array generated in an algorithm outside the loop. However I only want the Nx1 array that has just been generated.
Unfortunately, I cannot figure out how to resize, reshape or index the output array to do this.
I would like the loop to
give me out a 1D array after each iteration.
Any help would be greatly appreciated.

I hope I've understood your problem.
First your vi was lacking of the sub-vi working as shift register, I've replaced it with the rotate function.
The indexing of your arrays create a 2D array whose rows are your 1D array.To pick only one of them you have to use the index array function and select which one you want.
To use your temporary data in another part of your application you should use a local variable of array2.
I did it in a separated while loop That I syncronized with the for loop using occurrence, in this way the while loop runs each time a new value is inserted in array2 (each loop of the for loop structure).
If you don't need this syncronization just get rid of occurrence functions.
I place a delay in the for loop to show what happens when running.
Hope it was helpful.
Alberto Locatelli
Attachments:
array_test_v3.vi ‏35 KB

Returning multiple values with SELECT FOR LOOP

Oracle EE 11gR1
PL/SQL
OEL 5.8
===========
Would like to know how to do the following?
for x, y in (select name, street
from employees
where hire_date < sysdate - 100)
loop
In other words, is there a way to handle 2 (or more) values in a SELECT FOR LOOP structure? If not, then how to accomplish the same task.
The above does not work of course. :-)
Appreciate any and all advice.

Yes, just have one name in your for loop and that becomes the equivalent of a table name and reference the columns as that name.column name
for t in (select name, street
from employees
where hire_date < sysdate - 100)
loop
dbms_output.put_line('name = '||t.name);
dbms_output.put_line('street = '||t.street);
end loop;

Unable to put a timed structure in a parallel for loop, error -808

If I try to place a Timed Structure in a Parallel For Loop, the TS needs a different structure name per instance to prevent collisions. However, setting the Structure Name node to something unique per instance doesn't work, I get error -808. Have I missed something?
Thoric (CLA, CLED, CTD and LabVIEW Champion)

That got me thinking - something to do with the number of compiled parallel instances.
Indeed, the compiler creates a number of parallel instances of the for loop in the compiled code (in my case 8), and uses the number requested at the Parallel Instances terminal (just under the Iterations terminal), which is set to 2. Therefore the compiler has created 8 instances of the Timed Structure, each in its own for loop instance, but they all have the same defined Structure Name. When launched, there is an immediate conflict because they can't share the same name, and error -808 is launched before the set Structure Name function can change it. Hence the error still shows when requesting only one instance, because the other seven still exist.
I guess this means you can't have Timed Structures (or Timed Loops for that matter too) in a Parallelised For Loop?
Thoric (CLA, CLED, CTD and LabVIEW Champion)

Case Structure Nested in a For Loop

I have two pumps. I want one pump to be running and the other pump to be off. Then as soon as the first pump stops I want the other pump to start. I'd like this process to repeat as many times as I want. The code I have now uses a case structure inside a for loop. When the iteration is odd it is false and even is true this determines what case is carried out. Right now I have a code that can turn on one pump, stop it, and immediately start the second. However, after the second pump stops the first one does not start again. I've changed the number of iterations and I can't seem to get the process to continue. The program keeps running but the pumps stop doing anything. Attached is a file of my code as well as two image files (one showing true case and other showing false) of the same code.
Attachments:
Test Code 1.vi ‏31 KB
Case if True.png ‏37 KB
Case if False.png ‏35 KB

Your code has an inner while loop that checks for the status of the pump. Since you set up a target volume before the while loops start, I assume that it is what the status checks to determine when to stop the while loop.
When the the second iteration ends, has the volume for the first pump changed at all? If it is still the same, then the status is still at the target which means it will immediately stop after starting. You may also want to put some small wait statements inside the inner while loops so that the status isn't checked as fast as the CPU will allow it to run eating up CPU cycles.

Simple example - Break FOR loop inside an event structure based on Front panel event change.

I am running a for loop inside a state machine architecture that contains a FOR loop. How can I break this For loop based on Event change in front panel ??
Abhilash S Nair
Research Assistant @ Photonic Devices and Systems lab
[ LabView professional Development System - Version 11.0 - 32-bit ]
LabView Gear:
1. NI PXI-7951R & NI 5761
2. The Imaging Source USB 3.0 monochrome camera with trigger : DMK 23UM021
OPERATING SYSTEM - [ MS windows 7 Home Premium 64-bit SP-1 ]
CPU - [Intel Core i7-2600 CPU @ 3.40Ghz ]
MEMORY - [ 16.0 GB RAM ]
GPU - [ NVIDIA GeForce GT 530 ]
Attachments:
Case inside Event 3.vi ‏19 KB
Case inside Event.ctl ‏6 KB
Case inside Event 2.ctl ‏6 KB

Okay. Accpeting that the design is not favorable and not advantageous when my program expands. I have begin to follow producer/consumer programming architecture.
Please find the attached program which is a simple producer consumer with event structure. I wonder how could I stop looping around the producer and consumer loops over and over again. I am pretty sure that this ENQUEUE ELEMENT loops back to the consumer loop and starts from begining.
I hope my first program in PC architecture with State machine and Event structure is correct.
Abhilash S Nair
Research Assistant @ Photonic Devices and Systems lab
[ LabView professional Development System - Version 11.0 - 32-bit ]
LabView Gear:
1. NI PXI-7951R & NI 5761
2. The Imaging Source USB 3.0 monochrome camera with trigger : DMK 23UM021
OPERATING SYSTEM - [ MS windows 7 Home Premium 64-bit SP-1 ]
CPU - [Intel Core i7-2600 CPU @ 3.40Ghz ]
MEMORY - [ 16.0 GB RAM ]
GPU - [ NVIDIA GeForce GT 530 ]
Attachments:
Case inside Event 3.3-ProducerConsumer Event.vi ‏25 KB
Case inside Event.ctl ‏6 KB

Event structure in "for loop" and stacked sequence

I tried to put an event structure into a for loop sequence, then used a pause button to pause the program (one loop with event structure.vi). The pause button functioned normally since the program could be paused whenever the button was pressed. Then, I put this for loop sequence into a stacked sequence (Problem.vi), which has 2 frames and every frame has the for loop sequence in it. After the pause button was pressed once, the pause button and stop button will no longer effective anymore. Where should I modify so that this program will work properly? Thanks a lot.
Attachments:
Problem.vi ‏42 KB
one_loop_with_event_structure.vi ‏27 KB

Ah, at last something weird !
The answer is simple : don't do that !
You should either avoid having 2 event structures handling the same events, or learn how to process dynamic events.
Why didn't you read the answers to a question posted a few hours ago (still on the overview page of this forum ?). See here.
Chilly Charly (aka CC)
E-List Master - Kudos glutton - Press the yellow button on the left...

For loop, strings and case structures.

how do i pass out only a TRUE case string without passing the FALSE case? this is running in a FOR loop so im creating a string array, but i dont want empty elements where the default FALSE value has been tunneled out(ie the loop has N=5, so a string array of 5 elements is created) how can i end up with an array that contains only the TRUE case strings(ie N=5, but an array of only 2 elements)

You need to use an approach which doesn`t use auto-indexing the tunnel leaving the FOR loop. I have included an example.
Shane.
Using LV 6.1 and 8.2.1 on W2k (SP4) and WXP (SP2)
Attachments:
Case_statement-selective_array_build.vi ‏22 KB

How to pass the sequence number of current loop in a for loop in FPGA vi to the host

PCI-7830R
LV 8.2
What I was trying to do is to use multiple DIO to generate pulse at different sequence. Mode one is to automatically sweep from DIO1 to DIO20; mode 2 is several DIOs generate pulse simoutaneously. So I use a case structure to make the selection, in the mean time, I set up two for loop in each case so that I can use multiple pulse generations. For example, in scanning mode, if I set 2 exposures, it sweeps from 1 to 20 then do it again.
Then I need to get the loop sequence number, i of each scenario. So I put an indicator within the first loop, and create a local variable of it and put in the second one. Running the FPGA vi alone, I can see the indicator change in each case from 0 to N-1, N being the for loop time.But in the host vi, I tried to add this indicator as an element in the read/write invoke method, in the debugging mode, I could only see it directly jump to N-1 without all the changes I saw in FPGA vi.
Is it possible to get this number passed correctly from FPGA vi to the host vi? Thanks

Thanks for the reply Jared.
Excuse me if it looks incorrect, but I'm new to FPGA programming, so I would have to look into the FIFO you referred to. I used local variables because for one thing I have several different cases containing for loop in each of them, and I only want one indicator for the "i". If I put the indicator out of any for loop, it's only gonna show the last number which is N-1. For the other thing, it seems like property nodes are not allowed in FPGA vi. And by doing this, I can see the i number changing from 0 to N-1 in each case, well, in FPGA vi's front panel. But while I ran the host vi with everything, the indicator in host vi's front panel only showed the last number N-1. It may be the reason you said, it happened too fast before the indicator in host vi can catch it.
What I want to realize is to group the data I collect in host vi, for example, when I choose multiple exposure in each mode, and the FPGA runs 1 through 20 then do it again, I want the data stored in two groups using the loop sequence number as the seperator in file name. So it goes like 1-1, 2-1.......20-1; then 1-2, 2-2,.....20-2.

How do we use if statement in labview?moreover can i use if statement inside for loop?

how do we use if statement in labview?moreover can i use if statement inside for loop?

The if statement in LabVIEW is the Case structure. You can find that on the Structures palette right next to the For Loop. If you're still on the same subject about terminating a for loop early, then what you do is enclose your functions inside the loop with a case statment and make one of the case's empty except for one or more constants that you might have to wire. Hopefully, the attached picture will explain what I mean. Also, as I mentioned in one of your other posts, I think this technique is not as good as using a while loop. The array in the attached example is the same size no matter what and you may have to handle stripping extra or invalid elements.
Attachments:
For_Loop_with_Case.jpg ‏21 KB

Visa open and close with "for loops"

Hello everyone
In my program I used two "for loops" which include visa write and read for a RS32 port. it is not possible to close a devise with visa close as the out put is changed to 2D array!!! would you please help me with this error
Attachments:
ACU_232.png ‏108 KB

sam009 wrote:
Thanks for reply,
It works for "for loop" but what about "event structure loop" still is error for that.
Right-click on the output tunnel and uncheck "Use Default if Unwired". You will now be forced to wire the VISA Resource through each case.
There are only two ways to tell somebody thanks: Kudos and Marked Solutions
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Is there a way to run a For Loop independently within a While Loop in LabVIEW 2013?

In my program I would like to run a For loop inside of a While loop, and have them run independently, at their own execution rates. As a test, I wrote a simple VI with a While loop with 1 second timing, and into this I inserted a For loop with 3 second timing. I created indicators for both iteration terminals. Upon running the VI, I found the While loop waits for the For loop to run N times before the While loop executes again. I also found that sometimes the first iteration of the For loop will end at 1 second rather than 3 seconds, and the STOP button to terminate execution of the While loop does not always work.
Solved!
Go to Solution.

ksinks wrote:
Thanks, how would you synchronize the loops? I have gone through the Getting Started exercises and manual.
Why would synchronization matter? Did you want them to run independantly at their own speed or not?
Regardless, there's a synchronization pallette with functions for this, as Occurance.
Other solutions include a common loop counter and a case structure executing every X'th iteration, or having the faster loop send a queue or event every X'th loop that controls the slower loop.
/Y
LabVIEW 8.2 - 2014
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For Loop Structure

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