Using Arrays To Update Table Columns

Using Arrays To Update Table Columns

We are creating a lot of reports everyday and these reports contain a lot of data which is presented in various styles as per the requirements. The data that allows us to create the reports is usually referred as raw data and in most of the cases is stored in hidden sheets.

I am sure you all are aware of a feature called as Excel Tables OR Structured References in Excel. Excel Tables is (in my opinion) the best way to store your raw data and put Formulas in the columns where necessary, this way you eliminate the need of a Cell Based Reference formula (example =SUM(B4:B50) and replace them with =sum(YourTable[YourTableColumnName]).

Another good feature of the Excel Tables is you just need to put the formula in 1 cell and it is replicated for that column by Excel.

Sometimes these formulas take a lot of time to calculate when we have really huge data points. In this scenarios it is better to have hard-coded values instead of the formulas to gain on speed.
In this post we will learn about how we can make use of Array’s to quickly populate the excel columns with the desired results before publishing our reports and other documents.

Here is a demo of what I mean:

Below is the code that allows us to add a new column to our data table and then taking input from the Date Time column provides us with the Week Of column.

Sub UpdateWeek()
Dim myarray As Variant
Dim theRange As Range, startCellRow As Long
Dim tempStr As String
Dim myNewCol As ListColumn

‘If our column already exists then delete it
On Error Resume Next
Worksheets(“Data”).ListObjects(“cs”).ListColumns(“WeekOf”).Delete

‘adding our new column
Set myNewCol = Worksheets(“Data”).ListObjects(“cs”).ListColumns.Add
myNewCol.Name = “WeekOf”

‘Selecting the first cell of the column that contains our dates
Worksheets(“Data”).ListObjects(“cs”).ListColumns(“Date Time”).Range.Cells(2).Select

‘building a temporary Range address, this will be used to upload the entire range into the array

tempStr = ActiveCell.Address
startCellRow = ActiveCell.Row
tempStr = tempStr & “:$” & Mid(Sheets(“Data”).ListObjects(“cs”).ListColumns(“Date Time”).Range.Cells(2).Address, 2, 1) & “$”

tempStr = tempStr & LastRowInOneColumn(Mid(Sheets(“Data”).ListObjects(“cs”).ListColumns(“Date Time”).Range.Cells(2).Address, 2, 1))
‘loading the range into the array

myarray = Range(tempStr).Value

‘Looping through the array and converting each element to the relevant Week format
For i = LBound(myarray) To UBound(myarray)
myarray(i, 1) = Format(myarray(i, 1) – Weekday(myarray(i, 1), vbMonday) + 1, “ddd dd-mmm”)
Next

‘Setting the range address for our output column

Set theRange = Range(Cells(startCellRow, Worksheets(“Data”).ListObjects(“cs”).ListColumns(“WeekOf”).Range.Column), Cells(UBound(myarray) + (startCellRow – 1), Worksheets(“Data”).ListObjects(“cs”).ListColumns(“WeekOf”).Range.Column))
‘storing the values from our array to the WeekOf Column

theRange.Value = myarray
End Sub

Let’s Understand the code

We first delete the column if it is already existing to make sure we always get the new values as output. This is done by the below line of code.

Worksheets("Data").ListObjects("cs").ListColumns("WeekOf").Delete


Once we have deleted the column, we add it again as a blank column and change the name to “Week Of”.

Set myNewCol = Worksheets("Data").ListObjects("cs").ListColumns.Add
myNewCol.Name = "WeekOf"

After this we need to select the first cell of the column that contains the Date Time.

Worksheets("Data").ListObjects("cs").ListColumns("Date Time").Range.Cells(2).Select

Once we have selected the first cell of you Date Time column we then make use of the LastRowInOneColumn function to get the last row and create a range address. We use this range address to assign all the values contained in the Date Time column to an array.

tempStr = ActiveCell.Address
startCellRow = ActiveCell.Row
tempStr = tempStr & ":$" & Mid(Sheets("Data").ListObjects("cs").ListColumns("Date Time").Range.Cells(2).Address, 2, 1) & "$"

tempStr = tempStr & LastRowInOneColumn(Mid(Sheets(“Data”).ListObjects(“cs”).ListColumns(“Date Time”).Range.Cells(2).Address, 2, 1))
‘loading the range into the array
myarray = Range(tempStr).Value

Once we have loaded all the Date Time values into an array, we do a simple For loop to change the value in the array to the relevant Week Of

For i = LBound(myarray) To UBound(myarray)
myarray(i, 1) = Format(myarray(i, 1) - Weekday(myarray(i, 1), vbMonday) + 1, "ddd dd-mmm")
Next


We perform this operation on the same element and store the modified value in itself.
Once we have all these done, we need to define the Output range, that is where we need to the Week Of values to be stored. This is done by using the Range and Cell functions.

Set theRange = Range(Cells(startCellRow, Worksheets("Data").ListObjects("cs").ListColumns("WeekOf").Range.Column), Cells(UBound(myarray) + (startCellRow - 1), Worksheets("Data").ListObjects("cs").ListColumns("WeekOf").Range.Column))
'storing the values from our array to the WeekOf Column

theRange.Value = myarray

And lastly we assign all the values stored in the array to the new range address we have create above.

Download Demo File

Click here to download the demo file & use it to understand this technique.

What about you? Do you use them often? Please share your experiences, techniques & ideas using comments.

If you are new to VBA, Excel macros, go thru these links to learn more.

• What is VBA & Macros? Introduction
• Excel VBA Example Macros
• VBA tutorial videos

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About Vijay

Vijay (many of you know him from VBA Classes), joined chandoo.org full-time this February. He will be writing more often on using VBA, data analysis on our blog. Also, Vijay will be helping us with consulting & training programs. You can email Vijay at sharma.vijay1 @ gmail.com. If you like this post, say thanks to Vijay.