Combining Multiple Arrays in VBA - arrays

Question

I am currently trying to combine 46 arrays in to a single array. I have scoured the internet, to no prevail and am hoping someone here can help. I did find the below page, but I need to be able to look through each element of the new array in a nested for loop, so using the method below doesn't quite get me to my end goal.
Excel vba - combine multiple arrays into one
Basically, I need to combine my set of 46 arrays in such a way that I can then loop through each element using a nested for loop. ie.
Set of arrays:
myArray1 = (1, 2, 3, 4)
myArray2 = (5, 6, 7)
myArray3 = (8, 9)
myArray4 = (10, 11, 12, 13, 14)
.
.
.
myArray46 = (101, 102, 103)
Combine them to form new array:
myNewArray = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14... 101, 102, 103)
Loop through in nested for loop to check each element against my main array:
For i = LBound(mainArray) to UBound(mainArray)
For j = LBound(myArray) to UBound(myArray)
If mainArray(i) = myArray(j) Then
'do something
End If
Next j
Next i
Any help and/ or guidance with this is greatly appreciated!

Answer 1

Since you write in your comments that your end goal is to create an array of unique elements, you might be best served using a dictionary, where you can test for uniqueness as you add each element to dictionary. Something like:
Option Explicit
Function uniqueArr(ParamArray myArr() As Variant) As Variant()
Dim dict As Object
Dim V As Variant, W As Variant
Dim I As Long
Set dict = CreateObject("Scripting.Dictionary")
For Each V In myArr 'loop through each myArr
For Each W In V 'loop through the contents of each myArr
If Not dict.exists(W) Then dict.Add W, W
Next W
Next V
uniqueArr = dict.keys
End Function
Sub tester()
Dim myArray1, myArray2, myArray3, myArray4, myArray5
myArray1 = Array(1, 2, 3, 4)
myArray2 = Array(5, 6, 7, 8)
myArray3 = Array(9, 10, 11, 12, 13, 14)
myArray4 = Array(15, 16)
myArray5 = Array(1, 3, 25, 100)
Dim mainArray
mainArray = uniqueArr(myArray1, myArray2, myArray3, myArray4, myArray5)
End Sub
If you run Tester, you will see mainArray contains:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
25
100

Answer 2

Using your data this is how to create one array out of many:
Public Sub TestMe()
Dim myA, myB, myC, myD, myE
myA = Array(1, 2, 3, 4)
myB = Array(5, 6, 7)
myC = Array(8, 9)
myD = Array(10, 11, 12, 13, 14)
myE = Array(101, 102, 103)
Dim myCombine As Variant
Dim myNew() As Variant
Dim myElement As Variant
Dim myArr As Variant
Dim cnt As Long
myCombine = Array(myA, myB, myC, myD, myE)
For Each myArr In myCombine
For Each myElement In myArr
ReDim Preserve myNew(cnt)
myNew(cnt) = myElement
cnt = cnt + 1
Next
Next
For cnt = LBound(myNew) To UBound(myNew)
Debug.Print myNew(cnt)
Next cnt
End Sub
The "building" of the new array is facilitated through ReDim Preserve, which keeps the old values in the array whenver the dimension of the array changes. And if you want to do something with these arrays, you may use 3 nested loops (a bit slow) and have some check:
Dim cnt2 As Long
For cnt = LBound(myNew) To UBound(myNew)
For cnt2 = LBound(myCombine) To UBound(myCombine)
For Each myElement In myCombine(cnt2)
If myElement = myNew(cnt) Then
Debug.Print myElement & vbTab & " from " & vbTab & cnt2
End If
Next myElement
Next cnt2
Next cnt
This is what you get on the immediate window:
1 from 0
2 from 0
3 from 0
4 from 0
5 from 1
6 from 1
7 from 1
8 from 2
9 from 2
10 from 3
11 from 3
12 from 3
13 from 3
14 from 3
101 from 4
102 from 4
103 from 4

Answer 3

Alternate 'brick-by-brick' approach.
Option Explicit
Sub combineArrays()
Dim myArray1 As Variant, myArray2 As Variant, myArray3 As Variant
Dim myArray4 As Variant, myArray46 As Variant
ReDim mainArray(0) As Variant
myArray1 = Array(1, 2, 3, 4)
myArray2 = Array(5, 6, 7)
myArray3 = Array(8, 9)
myArray4 = Array(10, 11, 12, 13, 14)
'...
myArray46 = Array(101, 102, 103)
mainArray = buildMainArray(myArray1, mainArray)
mainArray = buildMainArray(myArray2, mainArray)
mainArray = buildMainArray(myArray3, mainArray)
mainArray = buildMainArray(myArray4, mainArray)
mainArray = buildMainArray(myArray46, mainArray)
ReDim Preserve mainArray(UBound(mainArray) - 1)
Debug.Print Join(mainArray, ",")
End Sub
Function buildMainArray(arr As Variant, marr As Variant)
Dim i As Long
For i = LBound(arr) To UBound(arr)
marr(UBound(marr)) = arr(i)
ReDim Preserve marr(UBound(marr) + 1)
Next i
buildMainArray = marr
End Function

Answer 4

The issue with using Redim Preserve to combine arrays is it can be an expensive operation, since you're basically re-creating the array everytime it's called. Since you have 46 arrays you're combining, you may very well be waiting a while.
Instead, you can loop over the arrays to figure out the total number of elements you need, dimension out your master array, then loop over the arrays again to do the actual assignment/merging. Something like this:
' encapsulates code to determine length of an individual array
' note that because arrays can have different LBounds in VBA, we can't simply use
' Ubound to determine array length
Public Function GetArrayLength(anArray As Variant) As Integer
If Not IsArray(anArray) Then
GetArrayLength = -1
Else
GetArrayLength = UBound(anArray) - LBound(anArray) + 1
End If
End Function
Public Function CombineArrays(ParamArray arraysToMerge() As Variant) As Variant
' index for looping over the arraysToMerge array of arrays,
' and then each item in each array
Dim i As Integer, j As Integer
' variable to store where we are in the combined array
Dim combinedArrayIndex As Integer
' variable to hold the number of elements in the final combined array
Dim CombinedArrayLength As Integer
' we don't initialize the array with an array-length until later,
' when we know how long it needs to be.
Dim combinedArray() As Variant
' we have to loop over the arrays twice:
' First, to figure out the total number of elements in the combined array
' second, to actually assign the values
' otherwise, we'd be using Redim Preserve, which can get quite expensive
' because we're creating a new array everytime we use it.
CombinedArrayLength = 0
For i = LBound(arraysToMerge) To UBound(arraysToMerge)
CombinedArrayLength = CombinedArrayLength + GetArrayLength(arraysToMerge(i))
Next i
' now that we know how long the combined array has to be,
' we can properly initialize it.
' you can also use the commented code instead, if you prefer 1-based arrays.
ReDim combinedArray(0 To CombinedArrayLength - 1)
' Redim combinedArray(1 to CombinedArrayLength)
' now that the combinedarray is set up to store all the values in the arrays,
' we can begin actual assignment
combinedArrayIndex = LBound(combinedArray)
For i = LBound(arraysToMerge) To UBound(arraysToMerge)
For j = LBound(arraysToMerge(i)) To UBound(arraysToMerge(i))
combinedArray(combinedArrayIndex) = arraysToMerge(i)(j)
combinedArrayIndex = combinedArrayIndex + 1
Next j
Next i
' assign the function to the master array we've been using
CombineArrays = combinedArray
End Function
To use this function, you'd do something like the following:
Public Sub TestArrayMerge()
Dim myArray1() As Variant
Dim myArray2() As Variant
Dim myArray3() As Variant
Dim myArray4() As Variant
Dim combinedArray As Variant
myArray1 = Array(1, 2, 3, 4)
myArray2 = Array(5, 6, 7)
myArray3 = Array(8, 9)
myArray4 = Array(10, 11, 12, 13, 14)
combinedArray = CombineArrays(myArray1, myArray2, myArray3, myArray4)
If IsArray(combinedArray) Then
Debug.Print Join(combinedArray, ",")
End If
End Sub
Regarding your last bit, that you're using an inner loop to combine the values in your final combined array: Your inner loop doesn't need to start at LBound(myArray). For any value of i, you've already compared it to the elements before it (e.g., when i = 2, it's already been compared to the first element). So you really just need:
For i = LBound(combinedArray) To UBound(combinedArray) - 1
For j = i + 1 To UBound(combinedArray)
' do whatever you need
Next j
Next i

Answer 5

Perhaps this ...
'To determine if a multi-dimension array is allocated (or empty)
'Works for any-dimension arrays, even one-dimension arrays
Public Function isArrayAllocated(ByVal aArray As Variant) As Boolean
On Error Resume Next
isArrayAllocated = IsArray(aArray) And Not IsError(LBound(aArray, 1)) And LBound(aArray, 1) <= UBound(aArray, 1)
Err.Clear: On Error GoTo 0
End Function
'To determine the number of items within any-dimension array
'Returns 0 when array is empty, and -1 if there is an error
Public Function itemsInArray(ByVal aArray As Variant) As Long
Dim item As Variant, UBoundCount As Long
UBoundCount = -1
If IsArray(aArray) Then
UBoundCount = 0
If isArrayAllocated(aArray) Then
For Each item In aArray
UBoundCount = UBoundCount + 1
Next item
End If
End If
itemsInArray = UBoundCount
End Function
'To determine the number of dimensions of an array
'Returns -1 if there is an error
Public Function nbrDimensions(ByVal aArray As Variant) As Long
Dim x As Long, tmpVal As Long
If Not IsArray(aArray) Then
nbrDimensions = -1
Exit Function
End If
On Error GoTo finalDimension
For x = 1 To 65536 'Maximum number of dimensions (size limit) for an array that will work with worksheets under Excel VBA
tmpVal = LBound(aArray, x)
Next x
finalDimension:
nbrDimensions = x - 1
Err.Clear: On Error GoTo 0
End Function
'****************************************************************************************************
' To merge an indefinite number of one-dimension arrays together into a single one-dimension array
' Usage: mergeOneDimArrays(arr1, arr2, arr3, ...)
' Returns an empty array if there is an error
' Option Base 0
'****************************************************************************************************
Public Function mergeOneDimArrays(ParamArray infArrays() As Variant) As Variant
Dim x As Long, y As Long, UBoundCount As Long, newUBoundCount As Long
Dim tmpArr As Variant, allArraysOK As Boolean
UBoundCount = 0
allArraysOK = True
For x = LBound(infArrays) To UBound(infArrays)
If Not IsArray(infArrays(x)) Or Not nbrDimensions(infArrays(x)) = 1 Then
allArraysOK = False
Exit For
End If
UBoundCount = UBoundCount + itemsInArray(infArrays(x))
Next x
If allArraysOK Then
ReDim tmpArr(0 To UBoundCount - 1)
UBoundCount = 0
For x = LBound(infArrays) To UBound(infArrays)
For y = LBound(infArrays(x)) To UBound(infArrays(x))
tmpArr(UBoundCount) = infArrays(x)(y)
UBoundCount = UBoundCount + 1
Next y
Next x
newUBoundCount = itemsInArray(tmpArr)
If newUBoundCount = UBoundCount Then
mergeOneDimArrays = tmpArr
Else
mergeOneDimArrays = Array()
End If
Erase tmpArr
Else
mergeOneDimArrays = Array()
End If
End Function

Answer 6

If you are working with one-dimensional arrays you could use a collection instead. It is much better at handling dynamic sizing.
You can declare a collection and then add each of the elements in the arrays to it. Then you will have one large list with all of the values.
Dim coll As New Collection
coll.Add MyArray(j)
Here is a good to collections introduction:
https://excelmacromastery.com/excel-vba-collections/