Index 2d array

Hi, I'm new to LabVIEW and I'm a bit stuck. I have a matrix that represents the grid of a table. Each part of the grid represents a section of the table that I would like to turn a valve on and off for. I have created a 2D array with the inputs for the valves. I have LabVIEW set up so that I have the array. However, I don't know how to assign the different positions in the array to the different valves (I already have the valves imported). I have looked at the index tool, but I don't understand how to use it for 2D arrays, nor do I understand how to create multiple outputs from the single index block. There are 128 ports, so if there is a way to automate the process, that would be preferable.

If you want to index a single elements of a 2D array, you need to wire both indices, else you get and entire row or column.
It is hard to give specific advice if you don't show us your code, but typically i might be easiest to use a FOR loop and autoindex over an array of valves and your array of booleans, for example. How are you talking to the valves?
Please attach a simplified version of your code. Thanks.
LabVIEW Champion . Do more with less code and in less time .

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Hi, thanks all your reply.
You may find "points_to_bar_graph.vi" from this website, I find it by this way.
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question.doc ‏520 KB
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Index an array of images only the last image shows

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and the vi:
Solved!
Go to Solution.
Attachments:
PulsedImageDisp1.vi ‏31 KB

Speed of what? The second loop can't run until the first loop is done, and all the operations are linear. I'm guessing you're referring to the perceived speed of displaying the images one after the other so you don't have to wait for the next image to be read which is why you pre-load all the images. Otherwise, the overall speed should be the same whether you use one loop or two. Actually, to be technically accurate, the two loop version will likely be a little slower overall since LabVIEW has to allocate more memory to store all the images, while in the one loop version it is only ever dealing with one image. If the images are large then you might actually run into a memory issue with the two-loop version (arrays need contiguous memory). Just something to keep in mind and to be careful about.

Show biggest index in array with value "True"

Hello,
Is it possible to show the maximum index number with value "true", like shown underneath?
I can show the value on what index the series of "true" ends with the "Array Max & Min" function, but when there is
one False between those True's, it will show the index of the True left of the False.
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File is attached
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Attachments:
Biggest index of array with value 1.vi ‏8 KB

Hi Stef,
here you go:
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You forgot the link.

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Hi 08,
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How to Use a Boolean Vector To Index an Array

Say I have an array A = [1 2 3 4 5 6 7 8 9 10].
I also have a boolean array B = [1 1 0 0 0 0 0 0 0 1].
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Anyone know a clean way of doing this?
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Solved!
Go to Solution.

This can be done with auto-indexing with conditional tunnels. The same approach could easily be applied to a 2D array, as well:

Iteration Speed issue when Indexing 3D array wried to a while-loop

Brief Description of my Program:
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Question on LabView:
How does indexing an 3D array which wires to the while-loop affect the speed of the loop iteration? I found that large dimension of sub-arrays in the 3D array slows down the iteration speed by comparing to indexing the same size of sub-array from smaller-sized sub-arrays of the 3D array to perform signal processing inside the while-loop. Why? Is there any other way of designing LabView Program to improve speed of iteration?
attachment:

Thank you all for your prompt replies and your interests. I am sorry about my attachment. But, I have now attached a jpg format image file as you suggested.
I had read the few papers on large data handling such as "LabVIEW Performance and Memory Management". Thus, I had already tried to avoid making unnecessary copies of data and growing arrays in my while-loop. I am not an expert on LabView, so I am not sure if the issues I have are just LabView fundamental limitations or there are any other ways to improve the iteration speed without reducing the input file size and DAQ output rate.
As you request, I also attach my top-level vi showing essential sections such as while-loop and its indexing. The attached file is as an image jpg format because the actual vi including Sub-VIs are as big as 3MB in total. I hope my attachment would be useful for anyone who would like to reply my question. If anyone would like to see my whole vi & llb files, I would be interesting to send it to you by an e-mail privately and thus please provide your e-mail address.
The dimension of my 3D array is N x 7 x M (Page x Row x Column), where N represents number of pages in 3D array, and M represents the size of 1D array. The file I am currently using forms 3D array of N = 28, & M = 10,731. Refering to the top-level vi picture I attached, my while-loop indexes each page per iteration and wrap-around. The sub-VI called "channel" inside the while-loop will further index its input (2D array) into seven of 1D arrays for other signal processsing. The output from that "channel" sub-VI is the superposition of those seven arrays. I hope my explaination is clear.
Attachement: 3Darray.jpg and MyVi.jpg
Kind Regards,
Shein
Attachments:
3Darray.jpg ‏30 KB
MyVI.jpg ‏87 KB

Error when indexing an array

HI
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Array_LV_PDA_82.JPG ‏126 KB

Hi Timo,
I didn't find the "string to unicode.vi" on my system, but I know, that unicode stores every character in 16bits. I suppose, if you index the next element in the array, you would get the expected 50. I think it would be more convenient to output an U16- Array in the "string to unicode.vi".
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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.
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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.
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1) Gather data
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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.

Why are date and time strings lost when indexing an array in a for loop

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failed array index.png ‏142 KB

Can you attach your VI with some typical values? (e.g. create in indicator on the 2D array, run your VI, then turn the indicator (now containing data) into a diagram constant). Place the FOR loop related code and that diagram constant into a new VI and attach it here.
How many times does the FOR loop run? Could it be that the last element of each 1D array is an empty string? (unless you put a wait inside the FOR loop, you'll never see the other elements in the probe)
LabVIEW Champion . Do more with less code and in less time .

Determine index of array within event structure

I am doing some testing with dynamically registered events. For these testing purposes, I have 2 separate arrays of boolean references hooked up to the dynamic input terminal. The event structure is executing like I expect it to. The only problem is that I want to know the index within the array for the event that triggered the value change event. I would have thought I could use the CtlRef node to determine this, but instead it returns a reference to the actual boolean control that triggered the event.
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That is a very good idea. The caption is good to use for the label you show to the user. You can change it to show different things, even programmatically, such as if you need to make your application more international and have it display controls in different languages to different users. It lets you use longer or more descriptive names, without having those long names eat up block diagram space.
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Drag and drop de index de array

se puede usar drag and drop en el idex de un array?
necesito arrastar el valor del index de un array y depositarlo en una celda de una tabla, e intentado con los ejemplos de drag and drop pero no me a funcionado y no se si se p ueda hacer esto en labview 2011.
si alguien tiene experiencia en estoy y me ayude.
gracias

solucionado.
tuve que identificar el index en la celda del array en que se dio clic y combinarlo con drag and drop

Boolean index of array

In Matlab often use a boolean array to access specific values in an array.
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I am trying to find a way to do this in a Mathscript node as otherwise the code takes ages to run.
Common code in Matlab and Mathscript:
a=[1,2,3,4,5]; %normally this is a much larger array
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c=b>0; %change b into boolean
d=[9,9,9,9,9];
The Matlab code is:
d(c)=a(c);
d
>>d=[1 9 3 9 5]
If I run the above in Mathscript I get the following error:
In Mathscript, to get the same "d" result I currently do:
for i=1:length(d)
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end
d
>>d=[1 9 3 9 5]
A slightly faster version is:
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Any ideas?
Thanks
Solved!
Go to Solution.

Hello,
The code you posted works fine in the MathScript node in LabVIEW 2009 as well as in the MathScript Window and the MathScript node in LabVIEW 8.6. As such, I will assume you are getting an error in the MathScript Window in LabVIEW 2009. We have already identified this issue and currently have filed bug report 151999 for it. The error message you are seeing did not come through in your post, so I assume it is -90026: "The indexes for a matrix indexing operation must be real, positive integers." The problem is that we are not treating the "c" indexing variable as a boolean. As such, this reports an error when it tries to use index 0 instead of a false. We are working on a fix for a future release.
As a workaround in the MathScript Window, you can use the find command in lieu of any boolean indexing. It should operate quicker than the loop implementation you reference. Instead of
d(c) = a(c);
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Grant M.
Staff Software Engineer | LabVIEW MathScript | National Instruments

Make index square array

I am writting a method that should create an array of 10 integers, where each element holds the square of its index number (thus, for example, myArray[3] should hold the value 9). Here is my code that does not work properly.
public int[] makeIndexSqArray(){
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Any suggestions?
Thank you ,
Peter

Before this line:
myArray[i] = myArray[i] * myArray;
include this
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Index 2d array

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