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What is the best way to have VBA count blank cells in a range?

Posted on 2010-08-31
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Last Modified: 2012-06-22
I have coded the following VBA to count blank cells in a range.  The cells contain formulas so i had to account for that but my code is too slow.

Column Q, R, S are phone numbers derived from trim operations and I am counting the cells without phone numbers.

Does anyone have a faster way to conduct this operation?


Dim MissingPhCt As Integer
Dim R as Integer

        Columns("T:V").Select
        Selection.Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
        
        Range("T2").Select
            For MissingPhCt = 1 To LastRow - 1
            R = MissingPhCt + 1
            
                ActiveCell.Offset(MissingPhCt - 1, 0) = WorksheetFunction.CountIf(Range(Cells(R, "Q"), Cells(R, "S")), "")
                  
            Next MissingPhCt
        
        Range("T1").Value = "Missing Phone #s"
        
        Range(Cells(1, 1), Cells(LastRow, LastCol + 3)).Select
        Selection.Copy

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Question by:Tony_Rhoades
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19 Comments
 
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Expert Comment

by:Dave Brett
ID: 33572616
Your COUNTIF is quick - that isn't the problem

The slow part of your code is the loop dumping the formulas cell by cell

A much faster technique would be to write your formulas in a single range

Can you pls post an actual sample

Cheers

Dave
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LVL 18

Expert Comment

by:Cory Vandenberg
ID: 33573855
As Dave suggested, get rid of the loop.

Replace this code:

            For MissingPhCt = 1 To LastRow - 1
            R = MissingPhCt + 1
           
                ActiveCell.Offset(MissingPhCt - 1, 0) = WorksheetFunction.CountIf(Range(Cells(R, "Q"), Cells(R, "S")), "")
                 
            Next MissingPhCt

With the snippet below.  I offer two solutions, one using copy/paste, one without it.  Can't test right now, so my apologies if one doesn't work.

Cheers,
WC
ActiveCell.Offset(1,0).Formula = "=COUNTIF(Q1,S1)"
ActiveCell.Offset(1,0).Resize(LastRow,)

'Or with copy/paste
ActiveCell.Offset(1,0).Formula = "=COUNTIF(Q1,S1)"
ActiveCell.Offset(1,0).Copy Destination:=Range(ActiveCell.Offset(1,0).Address,ActiveCell.Offset(LastRow,0).Address)

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Expert Comment

by:Cory Vandenberg
ID: 33573862
Oh, and if you don't want to store formulas on the sheet, use the PasteSpecial
ActiveCell.Offset(1,0).Formula = "=COUNTIF(Q1,S1)"
ActiveCell.Offset(1,0).Copy 
Range(ActiveCell.Offset(1,0).Address,ActiveCell.Offset(LastRow,0).Address).PasteSpecial xlPasteValues

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Accepted Solution

by:
calacuccia earned 500 total points
ID: 33574057
Also, don(t use ActiveCell, Activate or Select or Selection if you want quick & efficient

This should be much quicker with help of an array declared as variant at start of the procedure
Dim MissingPhCt As Integer
Dim R As Integer
Dim mArray As Variant
        
'LastRow = 142 --> This was not mentioned, just declared it for testing
        
Application.ScreenUpdating = False
Columns("T:V").Insert Shift:=xlToRight, CopyOrigin:=xlFormatFromLeftOrAbove
mArray = Range("T2:T" & LastRow).Value
For MissingPhCt = 1 To LastRow - 1
    R = MissingPhCt + 1
    mArray(MissingPhCt, 1) = WorksheetFunction.CountIf(Range(Cells(R, "Q"), Cells(R, "S")), "")
Next MissingPhCt
Range("T2:T" & LastRow) = mArray
Range("T1").Value = "Missing Phone #s"
        
Range(Cells(1, 1), Cells(LastRow, LastCol + 3)).Select
Selection.Copy
Application.ScreenUpdating = True

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LVL 17

Expert Comment

by:calacuccia
ID: 33575124
Range(Cells(1, 1), Cells(LastRow, LastCol + 3)).Copy is also better instead of lines 17/18 in the snippet above.
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LVL 33

Expert Comment

by:Norie
ID: 33575745
And this might be an idea too?

Range("A1").Resize(LastRow, LastCol+3).Copy
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Author Closing Comment

by:Tony_Rhoades
ID: 33577513
Thank you that works like a champ..  Also the added advice about using

Range(Cells(1,1), Cells(LastRow, LastCol +3)).copy

instead of .select and then selection.copy is much appreciated.  I will go back through all my code and clean this up as I imagine this simple change will improve the overall performace considerably.

Best Regards.
0
 
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Expert Comment

by:calacuccia
ID: 33577598
Thanks for the grade & good luck :-)
0
 
LVL 18

Expert Comment

by:Cory Vandenberg
ID: 33578259
I'm a little confused.  Yes, removing Select statements will improve efficiency, but removing the looping procedure would do more for code efficiency.  You are simply repeating a formula.  There is no need to loop through a range to do that.

To each his own. Glad you found something you're happy with.

WC
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Expert Comment

by:calacuccia
ID: 33578358
The improvement of my solution should not be the Select statements but the array operations and read/write operation of an array in one step.

But of course your solution should give tremendous improvement as well, I don't know which one would be quicker without have the real data: with your solution excel needs to calculate the formula's before being able to do the PasteSpeciaL
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LVL 18

Expert Comment

by:Cory Vandenberg
ID: 33579397
Ok, adding an array is better (remvoing repetitive copy/pastes), but I'm guessing for a small range the difference between your solution and mine is negligible.  For a large range, I would have to imagine removing the loop altogether would produce more efficient code.

Cheers,
WC
0
 
LVL 17

Expert Comment

by:calacuccia
ID: 33580131
Hi WC,

You are right, this was a test with 40k rows.
Array operation took 1,46875 seconds
Paste/PasteSpecial operation took 0,53125 seconds

With 500 rows, the result is the same
Array operation took 0,015625 seconds
Paste/PasteSpecial operation took 0,015625 seconds

However, I had to rewrite your code a bit :-)

In case the question asker is interested, this worked:


Range("T2").Select
ActiveCell.Offset(0, 0).Formula = "=COUNTIF(Q2:S2,"""")"
ActiveCell.Offset(0, 0).Copy
Range(ActiveCell.Offset(0, 0).Address, ActiveCell.Offset(LastRow - 2, 0).Address).PasteSpecial xlPasteFormulas
Range(ActiveCell.Offset(0, 0).Address, ActiveCell.Offset(LastRow - 2, 0).Address).Copy
Range(ActiveCell.Offset(0, 0).Address, ActiveCell.Offset(LastRow - 2, 0).Address).PasteSpecial xlPasteValues

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LVL 18

Expert Comment

by:Cory Vandenberg
ID: 33580406
calacuccia,

Ya, I wasn't certain the PasteSpecial xlPasteValues would work without first pasting the formulas.  It was late last night when I posted that.

If you are looking for truly efficient clean code, the following would be my best suggestion.

Cheers,
WC
Sub test()
    Dim rng As Range
    Dim LastRow As Long
    
    LastRow = 40000
    Set rng = Range("T2:T" & LastRow - 2)
    rng.Formula = "=COUNTIF(" & Cells(rng.Row, rng.Column - 3).Address(False, False) & ":" & Cells(rng.Row, rng.Column - 1).Address(False, False) & ","""")"
    rng.Copy
    rng.PasteSpecial xlPasteValues
End Sub

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LVL 17

Expert Comment

by:calacuccia
ID: 33580461
Yep, it helps a bit :-) (40k rows)

Array operation took 1,484375 seconds
Paste/PasteSpecial operation took 0,53125 seconds
Efficient Paste/PasteSpecial operation took 0,515625 seconds
0
 
LVL 18

Expert Comment

by:Cory Vandenberg
ID: 33580601
:) I didn't just mean efficient in processing time, but also in typing the code and comprehending it later.

See ya around,
WC
0
 

Author Comment

by:Tony_Rhoades
ID: 33581054
Guys thank you for the continued interest in this question I have learned a lot.  I incorrectly assumed the array would be more efficent time wise.

I will however defer to the Clock and use WarCrimes  solution.  09/01/10 12:23 PM, ID: 33580406

Thanks Again.

Tony
0
 
LVL 18

Expert Comment

by:Cory Vandenberg
ID: 33581164
A range object in Excel is essentially an array, in the Object-Oriented sense of the word.

The difference in efficiency isn't that I'm not using an array, it's that I'm not using a loop.  In essence, I'm copying an array to an array when I write the Formulas, where as the accepted solution is merely writing one formula at a time to the array position, then copying the array.  This is where the lack of efficiency comes in and why we see a time discrepency on larger datasets but not smaller ones.

Cheers,
WC
0
 

Author Comment

by:Tony_Rhoades
ID: 33581280
Thank you for making this clear.  I will keep this in mind for the rest of my code.

Best

TR
0
 

Author Comment

by:Tony_Rhoades
ID: 33595681
I have posted a question about parsing my data and It now occurs to me that this conversation may apply.  

Would you all mind looking at question 09/01/10 01:48 PM, ID: 26445592 "Looking for a better way to parse my data?"
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