write delimited spreadsheet

[LED47]

I'm embarrassed to ask this but I'm terribly rusty with LabVIEW

If I'm outputting a 2D array into the file (Double precision numbers) Every for loop cycle

1 4
2 5
3 6
Using -write delimited spreadsheet Function

I get

1 4
2 5
3 6
1 4
2 5
3 6

After two cycles

What I want

1 4 1 4
2 5 2 5
3 6 3 6

How do I bring the second cycle back to the top of the file in alignment with the first data set?

[Darren]

If performance isn't a concern, you could read the existing contents of the file, do some transposes, and then append the new array.

[cordm · Accepted solution]

You can only append rows, not columns. This is a consequence of the file layout.

On disk, the file looks like

1 4\n2 5\n3 6\n

after inserting columns, the file looks like

1 4 1 4\n2 5 2 5\n3 6 3 6

You need to build a larger 2D array in memory by concatenating each cycle’s 2D array horizontally (column-wise), then write the final array to the file once.

build array columnwise

The alternative is to change the file layout. Or rewrite the file each iteration.

[LED47]

That's the ticket...

Thank you to everyone

[altenbach]

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@cordm wrote:

The alternative is to change the file layout.

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I agree, change your code to append two rows with each iteration and document it. Even for a gigantic file, no existing data needs to ever be touched.

In particular, use low-level file i/o, open it before the loop, keep appending in the loop, and close when done.

You can always add a postprocessing step that generates the transposed file at the very end.