topic Re: Need help with 2D array in LabVIEW

Need help with 2D array

aveo — Wed, 12 Mar 2014 05:16:03 GMT

Hi All,

I am working with a 2D array which stores numeric values. Let me explain my problem with an example.

consider a 2D array as shown in the attached image(input.png). the elements in the 2nd row are already present

in the 1st row. How can i obtain a new 2d array in which the rows, which are already a subset of some other

row, are not present i.e., each row has unique elements only.(output.png)

Thank you for the help.

Regards

Aveo

Re: Need help with 2D array

altenbach — Wed, 12 Mar 2014 05:23:00 GMT

Are the non-duplicate element values always increasing in memory order? That would simplify certain things.

I would (1) reshape to a 1D array, (2) remove all duplicates, (3) then reshape back to a 2D array of the original size.

Re: Need help with 2D array

aveo — Wed, 12 Mar 2014 05:43:39 GMT

Hi,

Thank you for the quick reply.

YES, the non-duplicate element values always increase in memory order.

However the 2d array could be like this also: 1 2 3 4 5 6 8 9

2 5 6 8 0 0 0 0

5 8 0 0 0 0 0 0

7 0 0 0 0 0 0 0

Regards

Aveo

Re: Need help with 2D array

altenbach — Wed, 12 Mar 2014 06:24:11 GMT

@aveo wrote:

YES, the non-duplicate element values always increase in memory order.

However the 2d array could be like this also: 1 2 3 4 5 6 8 9

2 5 6 8 0 0 0 0

5 8 0 0 0 0 0 0

7 0 0 0 0 0 0 0

Well, in this example they don't increase in memory order (e.g. 8 occurs before the first 7). Do you want them sorted in the output array in this case or in the original order of first occurrence. (It does not help if you describe a special case, but then fail to show what the desired output would be ;))

If you want the output sorted, do bascally what I suggested above.

Remove all duplicate elements or elements that are zero. (here are some ways to do it, some are much more efficient ;)). Of course you would need to add code to also remove zeroes. Should be trivial to change. Good luck. 😄

Re: Need help with 2D array

aveo — Wed, 12 Mar 2014 06:32:22 GMT

Thanks for the suggestions. 🙂

I will implement them and post it here.

Regards

Aveo

Re: Need help with 2D array

aveo — Thu, 13 Mar 2014 12:08:44 GMT

Hi Altenbach,

Thanks for your suggestions.

I have created a vi (Find_Overlapping_Rows.vi) that does what i require, however in a different way.

can you suggest any more improvements in it?

Thanks.

Regards

Aveo

Re: Need help with 2D array

altenbach — Thu, 13 Mar 2014 15:54:54 GMT

Put some typical numbers in the input array, make the current values default, save and attach the toplevel VI once more.

... and yes, this looks way too complicated. Can there be negative values too?

Re: Need help with 2D array

altenbach — Thu, 13 Mar 2014 16:05:20 GMT

Here's what I had in mind....

Re: Need help with 2D array

aveo — Fri, 14 Mar 2014 04:38:46 GMT

Hi Altenbach,

I am attaching the vi again with an initialized array.

I put the same array in your vi and the results are different.

If you will take a look at the array the 6th row(starting from 0) has 10 and is not a subset of any other row.

However in Find_Overlapping_Rows_MODCA.vi it is not coming as i want it.

And there cannot be negative values.

Thanks.

Regards

Aveo

Re: Need help with 2D array

altenbach — Fri, 14 Mar 2014 06:20:30 GMT

aveo wrote:
However in Find_Overlapping_Rows_MODCA.vi it is not coming as i want it.

Then you need to define better what you want. There are millions of possible results that are different from what I did, so we cannot narrow it down at all given the vague information. What is the exact result you want from your VI when run with the current default input data?

Maybe you should manually fill the output array with the exepcted result and also make it the default.

Re: Need help with 2D array

altenbach — Fri, 14 Mar 2014 06:33:07 GMT

aveo wrote:
If you will take a look at the array the 6th row(starting from 0) has 10 and is not a subset of any other row.

However in Find_Overlapping_Rows_MODCA.vi it is not coming as i want it.

OK, it is a complete mystery where else you exepct the "10" to appear in the output array. Here's what I get with my code.

We cannot solve a problem unless it is fully defined. Currently it is not!

Re: Need help with 2D array

aveo — Fri, 14 Mar 2014 07:47:32 GMT

The 10 should appear in a new row (and not with 8,9). This is because, if you take a look at the input array,

10 is not present in the row where 8,9 is.

You can see the required output if you run my code( Find_Overlapping_Rows.vi) with the same array.

Guess my problem can be solved if i use my vi only.... but sadly it is complicated. i thought i would be able to

make something more simple 😞

My apologies that i am still unable to clearly explain the problem statement to you.

let me breakdown the problem with this example.

consider the input array 1 2 3 4 5 6 7

2 3 6 0 0 0 0

3 2 7 0 0 0 0

4 5 0 0 0 0 0

7 1 0 0 0 0 0

8 9 0 0 0 0 0

10 0 0 0 0 0 0

the 2,3,6 in 2nd row is already found in 1st row so delete 2nd row.

the 3,2,7 in 3rd row is already found in 1st row so delete 3rd row.

the 4,5 in 4th row is already found in 1st row so delete 4th row.

the 7,1 in 5th row is already found in 1st row so delete 5th row.

the 8,9 in 6th row is not found in any other rows so retain it.

the 10 in 7th row is not found in any other rows so retain it.

thus the output array must have.

1 2 3 4 5 6 7

8 9 0 0 0 0 0

10 0 0 0 0 0 0

Hope i have cleared it a little bit now.

Thanks for all the help and quick reply 🙂

Regards

Aveo

Re: Need help with 2D array

altenbach — Fri, 14 Mar 2014 07:53:42 GMT

OK, now it is clearer. Unfortunately it is 1am here, so I will look tomorrow. I am sure this can still de done with much less code! 🙂

Are these alway small integers? What is the range of values that can occur overall. How long can the rows be?

Re: Need help with 2D array

altenbach — Fri, 14 Mar 2014 08:09:53 GMT

OK, try this:

(assuming the integers are all <100, modify as needed.)

Re: Need help with 2D array

aveo — Fri, 14 Mar 2014 09:07:37 GMT

Hi Altenbach, Yes this is what i was looking for! 🙂 The rows will be between 200 or 300 at most.

This works amazingly without complicating the program. Thanks a mighty lot for this. 🙂

Regards

Aveo

Re: Need help with 2D array

altenbach — Fri, 14 Mar 2014 15:09:50 GMT

Yes, then you simply need to increase the lookup array size a little bit. Even if there is no known upper limit for the numbers, the code would not be much more complicated, but we would need to change the code a little bit.

SImple problems always have simple solutions! 😄 Note the use of the "-1". This is to automatically ignore all zeroes.