Comments on: Combining Arrays

By: Maurik van den Heuvel

Maurik van den Heuvel — Sat, 02 Jan 2010 22:38:00 +0000

Hi, I went throught Juan Pablo's code. I had not worked with arrays very often yet, and I like the simplicity of this code. I was wondering, if you'd want to not add the 2nd vector below the first vector, but as a new column, how would you code that?

Really curious to know!

Thanks, Maurik

By: Charles Williams

Charles Williams — Mon, 06 Oct 2008 18:51:00 +0000

Hans,

Having tested it I think the result of your one-liner is always a variant containing strings, which could be unfortunate if you were feeding it numbers.

I agree that most of the time the speed difference does not matter, but for larger data volumes the speed difference could be significant.
If you built a UDF that combined 2 10000 element arrays and had 1000 instances of the udf the time difference on my fast machine would be about 20 seconds.

regards
Charles

By: Hans Schraven

Hans Schraven — Sun, 05 Oct 2008 22:18:00 +0000

Although 'join' converts to a string, split results in an array (Variant). So there's no use in declaring strings.
I combined 2 arrays consisting of 100 elements to an array of 200 elements.
My one-liner took 1,3 msec, the 'loop' did it in ,3 msec.( test performed on a very slow computer PII, 350 MHz)
Although the difference in speed amounts to a factor 4, no user will notice the difference.

By: Charles Williams

Charles Williams — Sun, 05 Oct 2008 19:12:00 +0000

Hans,

I think your code always converts to strings?

And since string handling, particularly declaring strings, is usually very inefficient in VBA I would guess using Split and Join is slow. Have you done any tests?

regards
Charles

By: Hans Schraven

Hans Schraven — Sat, 04 Oct 2008 15:35:00 +0000

I'd prefer

arrayunion=split(join(va1,"|") & "|" & join(va2,"|"),"|")

By: Andrew Chien

Andrew Chien — Fri, 03 Oct 2008 04:53:00 +0000

Two comments:
(1) the checking of Empty array does not work,
TypeName() of an NOT allocated dynamic array of integer will return "Integer()"

2) the for-loop to copy the second array: the LBound of second array is not always one, suggest to change to
va1(Upper + (i-LBound(va2)+1) = va2(i)

regards

By: Colo

Colo — Fri, 06 Aug 2004 03:50:00 +0000

I've added a similar UDF in my tips site.
Thanks for giving me an idea!
http://puremis.net/excel/code/076.shtml

By: Colo

Colo — Thu, 05 Aug 2004 08:21:00 +0000

Hi Jamie,

I'm afaraid the arguments must be an array. Please give this a try.

Sub TestingFunction()
Dim ele
a = Array(1, 2, 3)
b = Array(4, 5, 6)
c = ArrayUnion(a, b)
For Each elm In c
Debug.Print elm
Next
End Sub

Hi Dick, I placed a link to here on my tip site, see
http://puremis.net/excel/code/075.shtml

By: Jamie Collins

Jamie Collins — Mon, 02 Aug 2004 18:32:00 +0000

I've tested this in the Immediate Window, here are the results:

a = Array(Sheet1)
b = Array(ThisWorkbook)
c = ArrayUnion(a,b)
? err.Description
Object doesn't support this property or method

Jamie.

By: Dick

Dick — Mon, 02 Aug 2004 17:58:00 +0000

Stephen: I’ve tried that same thing when I wanted a generic array sorting routine that would handle any number of dimensions. After a while, I decided that it was easier to have two routines; one for single dimension arrays and one for double dimension arrays. I have yet to use a three dimension array. It might be worth another look, though.