Functions that return arrays

[Pflugs]

I am trying to a UDF that uses arrays and worksheet matrix functions to
calculate the intersection of three spheres. I have declared several 1- and
2-D double arrays to store data.

I originally declared these array variables as doubles, but I found I could
not use functions like the following example:

Dim tempMatrix(1 to 3, 1 to 3) as Double
tempVector = identity(tempVector)

where "identity" is a UDF that accepts a square array and sets it to an
identity matrix. I imagine that I cannot assign the function's return to
tempVector because it is a double array, not a Variant (i.e. not an object).

I declared these variables as Doubles because I have read that variants are
slow and inefficient and should be avoided if possible. How then would be
the best way to fill these variable? Should I use subroutines and send the
double array as a parameter? Or should I use variant arrays?

But then, variant arrays cannot be initialized with dimensions, right? I.e:

Dim tempVector(1 to 3, 1 to 3) as Variant

I'm looking for the Best Practice here. Thanks.
Pflugs

 

[Tom Ogilvy]

Use variants since that is what is required to do what you want.

Dim tempVector as Variant
ReDim tempVector(1 to 3, 1 to 3)

 

[Pflugs]

How do I use the matrix functions with varaint arrays? Do I first have to
create a similar double array?

 

[Alan Beban]

I don't vouch for "best practice", but if the functions in the freely
downloadable file at http://home.pacbell.net/beban are available to your
workbook, you might consider

Assign identity(tempVector), tempVector

Alan Beban

 

[Tom Ogilvy]

If you have to use a double, then adjust your identity function so it isn't a
function but a subroutine.

Arrays are passed by reference, so if you work on it in the identity
function, you don't have to "return" it. Just call your Identity sub with
the tempVector as an argument

sub Main()
Identity TempVector
' now just use the altered tempVector

end sub

Public sub Identity( t() as Double )
' code that alters "t"
' no code like Identity = t
End sub

 

[Dana DeLouis]

where "identity" is a UDF that accepts a square array and sets it to an

identity matrix.

Instead of using two loops, here's something I might use:

Sub MainCode()
Dim m As Variant
m = IdentityMatrix(3)
End Sub

Function IdentityMatrix(n)
IdentityMatrix = Evaluate(Replace("--(ROW(#)=COLUMN(#))", "#",
[A1].Resize(n, n).Address))
End Function