array declaration in excel code example
Example 1: vba array
'VBA arrays can be fixed-size (static) or resizable (dynamic).
'This is determined when the array is declared:
Dim vArrA() 'dynamic: size is determined later.
Dim vArrB(1 to 5) 'static: size is determined now and cannot be changed.
'Array size refers to the number of elements in the array. For example, vArrB()
'above has five elements. The "1 to 5" is referred to as the array's range of
'indices. The range size must be positive, meaning the number of elements must
'be positive. This means that the 2nd integer in the range must be greater
'or equal to the first integer.
'VBA is unusual among programming languages with regards to the lowerbound or
'the base, of arrays. Most languages require arrays to have a base (or lowerbound)
'of zero. VBA arrays can have lowerbounds of ANY Long Integer value
'(-2147483648 through +2147483647). So, all of the following are valid:
Dim vArrC(0 to 9)
Dim vArrD(1 to 10)
Dim vArrE(11 to 20)
Dim vArrF(-8877 to -8868)
Dim vArrG(-5 to 4)
'vArrC through vArrG are perfectly legal and each has precisely 10 elements. Note
'that the size AND the bounds are fixed for static arrays. Both of these
'attributes can be changed for dynamic arrays whenever the need arises:
ReDim vArrA(1 to 1000)
'And at a later point:
ReDim vArrA(0 to 4)
'A third attribute of VBA arrays is the number of dimensions. Every example on
'this page thus far represents a 1D array. Another term for a one-dimensional
'array is vector. A vector does not really have rows or columns, just
'elements.
'However, when writing a 1D array to a worksheet, Excel treats the array as if
'it were a 2D array consisting of 1 row and n colums (where n is equal to the
'number of elements). This fact causes confusion for many.
'Consider:
ReDim vArrA(1 to 5)
vArrA(1) = "m"
vArrA(2) = "n"
vArrA(3) = "o"
vArrA(4) = "p"
vArrA(5) = "q"
Sheet1.Range("A1:E5") = vArrA
'Sheet1 now has the following values:
' A B C D E
'1 m n o p q
'2 m n o p q
'3 m n o p q
'4 m n o p q
'5 m n o p q
'This is why Transpose() is required to write the 1D array vertically:
Sheet1.Range("A1:E5") = WorksheetFunction.Transpose(vArrA)
'Sheet1 now has the following values:
' A B C D E
'1 m m m m m
'2 n n n n n
'3 o o o o o
'4 p p p p p
'5 q q q q q
'Notice that the one array with five elements can be written to multiple rows
'or with Transpose() to multiple columns. Of course, the array can be
'written to one row:
Sheet1.Range("A1:E1") = vArrA
'Or to one column:
Sheet1.Range("A1:A5") = WorksheetFunction.Transpose(vArrA)
'Since Excel treats 1D arrays (vectors) oddly when writing to a worksheet, it
'can be easier to work with 2D arrays. In Excel VBA, 2D arrays are row major.
'This means that rows are represented by the first dimension and columns are
'represented by the second.
ReDim vArrA(1 to 5, 1 to 10)
' ^rows ^cols
'vArrA is now sized as a 2D array with 5 rows of 10 columns. It can be written
'to a worksheet with 5 rows of 10 columns without using Transpose().
'Size, lower and upper bounds, and number of dimensions
'are all fixed for static arrays and they are all specified when the array is
'declared:
Dim vArrH(0 to 9, 1 to 10)
'vArrH is a static 2D array of 100 elements, 10 rows of 10 columns, with
'0 as the lowerbound for the first dimension (the rows) and 1 as the lowerbound
'of the second dimension (the columns). None of these attributes can later
'be changed for vArrH, since it is a static (or fixed) array. In contrast,
'all three of these attributes can be changed for a dynamic array... at any time.
'The max number of dimensions supported for an array is 60, though
'it is unusual to use arrays with more than 3 dimensions. Conceptually, a
'1D array is a vector, a 2D array can be thought of as a worksheet with rows
'and columns, a 3D array can be thought of as a workbook with multiple
'worksheets (or a cube), and a 4D array can be thought of a folder of workbooks
'(or perhaps a hypercube). But keep in mind that each dimension can be declared
'with a different number of elements. For example, a 4D dynamic array:
ReDim vArrA(0 to 4, 1 to 10, 3 to 7, 1 to 2)
' ^rows ^cols ^sheets ^books
'A fourth attribute of arrays is the data type. VBA's default data type
'is the Variant. If no data type is specified then by default the data type is actually Variant. So all the
'examples so far are Variant arrays, that is an array where every single element
'is of data type Variant.
'Here are some other data type array examples. They can be written verbosely
'or in some cases with a type declaration character:
Dim a() As Double 'or... Single, Short, Long, Currency, String, Byte, Date
'or... Boolean, UserDefinedType, ClassName, Object
Dim a#() 'or... a!(), a%(), a&(), a@(), a$()
'Note: 64bit VBA also includes the LongLong data type:
Dim a() As LongLong 'or... a^()Example 2: excel vba reset array to zeros fastest way
'In VBA to reset a dynamic array of Longs or Doubles to all zeros, the simplest way
'is to use the Redim() function. It's also extremely fast, roughly four times
'faster than iterating over the array to set each element.
Sub Test_ArrayZeroing()
Dim i&, k&, a() As Long
Dim time1#, time2#
k = 100000000 '<--100 million elements
ReDim a(1 To k)
For i = 1 To k: a(i) = i: Next '<--Fill array
time1 = Timer
'For i = 1 To k: a(i) = 0: Next '<--Method 1: 1125 ms
ReDim a(1 To k) '<--Method 2: 260 ms (easy and faster)
time2 = Timer
Debug.Print "Test_ArrayZeroing: " & (time2 - time1) * 1000
End Sub
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
'If you are willing to use an external call to Windows then an much faster
'method exists:
Private Declare PtrSafe Sub AssignZero Lib "kernel32" Alias "RtlZeroMemory" (pDst As Any, Optional ByVal CB& = 4)
Sub Test_ArrayZeroing()
Dim i&, k&, a() As Long
Dim time1#, time2#
k = 100000000 '<--100 million elements
ReDim a(1 To k)
For i = 1 To k: a(i) = i: Next '<--Fill array
time1 = Timer
'For i = 1 To k: a(i) = 0: Next '<--Method 1: 1125 ms
'ReDim a(1 To k) '<--Method 2: 260 ms
AssignZero a(1), k * 4 '<--Method 3: 74 ms (super fast)
time2 = Timer
Debug.Print "Test_ArrayZeroing: " & (time2 - time1) * 1000
End Sub
'Note that when using AssignZero() with an array of Doubles, remember that
'Doubles require 8 bytes of memory each, as opposed to the 4 bytes required
'for Longs.
'So the call to AssinZero() would like this for and array of Doubles:
AssignZero a(1), k * 8
'Note that the first argument of AssignZero() should be the first element
'of the array to be reset to zeros. The lowerbound in the above examples is 1,
'but your array may have a lowerbound of 0... or some other number.
'Note that all three methods here work for arrays of Longs and Doubles. But to
'zero out an array of Variants, the only option is Method 1. This is because
'the default value for a Variant is EMPTY, not zero... and AssignZero() will
'not work because Variants store and require metadata in addition to
'the value... and that metadata would be wiped out by AssignZero().
'Note that to reset an array to some value other than zero, the only
'option is to use Method 1.
'Note that this entire post is about Dynamic arrays. If you wish to zero out a Static
'array of Longs or Doubles you may also use the 'Erase' statement:
Erase a
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