Please Note: This article is written for users of the following Microsoft Excel versions: 97, 2000, 2002, and 2003. If you are using a later version (Excel 2007 or later), this tip may not work for you. For a version of this tip written specifically for later versions of Excel, click here: Calculating the Interval between Occurrences.

Calculating the Interval between Occurrences

by Allen Wyatt
(last updated December 5, 2015)

2

Roger asked if there was a way to calculate the interval between occurrences of values in a list. For instance, he has several thousand numbers in column A. Looking at the value in cell A351, the last time that value occurred in the list was in cell A246. He would like a formula that could be placed in cell B351 and return 105, the difference between 351 and 246.

This approach is difficult to implement in Excel because Excel is not very good at searching backwards—up a column. If the premise could be reversed, then the task becomes much simpler. For instance, if a formula in cell B246 could return the value 105, indicating the interval until the next occurrence of the value in cell A246, instead of calculating the last occurrence. The following formula calculates the next occurrence of the value in cell A1:

=MATCH(A1,A2:$A$65536,0)

Place this formula in cell B1 and copy it down however many cells are necessary. If the value in column A does not occur again in the column, then the formula returns the #N/A error. If you would rather have the formula return 0, then the following works:

=IF(ISNA(MATCH(A1,A2:$A$65536,0)),0,MATCH(A1,A2:$A$65536,0))

If you absolutely must count upwards (find the previous occurrence instead of the next occurrence), then the easiest way to do it is with a user-defined function. The following function, RowInterval, will look backward through a range you specify and return the desired interval:

Function RowInterval(TestCell As Range, LookHere As Range) As Long
    Dim varValue As Variant
    Dim lngRow As Long

    Application.Volatile
    varValue = TestCell.Value
    
    'Check for occurrences of the test value in the search range
    If WorksheetFunction.CountIf(LookHere, varValue) > 0 Then
        With LookHere
            'Get the last row of the search range
            lngRow = .Row + .Rows.Count - 1
            'Start with the last cell in the search range and work up
            Do Until .Item(lngRow, 1).Value = varValue
                lngRow = lngRow - 1
            Loop
        End With
        'Subtract the number of the row containing the found occurrence
        'from the number of the row containing the test value
        RowInterval = TestCell.Row - lngRow
    End If
End Function

In order to use the function, you would put the following formula in cell B2, and then copy the formula down the number of desired cells:

=RowInterval(A2,A$1:A1)

ExcelTips is your source for cost-effective Microsoft Excel training. This tip (2338) applies to Microsoft Excel 97, 2000, 2002, and 2003. You can find a version of this tip for the ribbon interface of Excel (Excel 2007 and later) here: Calculating the Interval between Occurrences.

Author Bio

Allen Wyatt

With more than 50 non-fiction books and numerous magazine articles to his credit, Allen Wyatt is an internationally recognized author. He  is president of Sharon Parq Associates, a computer and publishing services company. ...

MORE FROM ALLEN

Making Revisions

You've turned on Highlight Changes, but how do you know what has been changed? This tip explains how Excel displays those ...

Discover More

Confirming File Conversions

Open a file that isn't a Word document and Word will still try to convert it to a Word document. If you want Word to let you ...

Discover More

Numbering with Sequence Fields

One of the most powerful and versatile fields you can use in Word is the SEQ field. This tip shows how you can use the field ...

Discover More

Excel Smarts for Beginners! Featuring the friendly and trusted For Dummies style, this popular guide shows beginners how to get up and running with Excel while also helping more experienced users get comfortable with the newest features. Check out Excel 2013 For Dummies today!

More ExcelTips (menu)

Saving Common Formulas

It is not uncommon to reuse formulas in a variety of workbooks. If you develop some "gotta keep" formulas, here are some ...

Discover More

Formulas Don't Calculate as Formulas

Enter a formula (starting with an equal sign) and you may be surprised if Excel doesn't calculate the formula. Here's a good ...

Discover More

Creating an Amortization Schedule

An amortization schedule is a report that shows how the outstanding balance on a loan changes with payments made over time. ...

Discover More
Subscribe

FREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."

View most recent newsletter.

Comments

If you would like to add an image to your comment (not an avatar, but an image to help in making the point of your comment), include the characters [{fig}] in your comment text. You’ll be prompted to upload your image when you submit the comment. Images larger than 600px wide or 1000px tall will be reduced. Up to three images may be included in a comment. All images are subject to review. Commenting privileges may be curtailed if inappropriate images are posted.

What is seven minus 1?

2015-12-06 10:09:37

Michael (Micky) Avidan

To my opinion (if I manage to correctly understand the task) the suggested "Array Formula" (No helper column) in the attached linked picture should do.
http://screenpresso.com/=nBUje
--------------------------
Michael (Micky) Avidan
“Microsoft® Answers" - Wiki author & Forums Moderator
“Microsoft®” MVP – Excel (2009-2016)
ISRAEL


2015-12-05 10:28:25

Fred Burg

Hi Allen,

It's not totally clear what Roger needs. Can the contents of A246 and A351 change?

For example, suppose A351 contains the word "Class" and the last time that occurred was in A246 and neither cell would change.

If that's the case, this is easy. If A351 can change to, for example, "Rooms" and Roger now wants to know when that last occurred, that is harder.

Going back to my first scenario (which I actually use), add a hidden column B with a formula such as
=if(A1="Class",ROW(),0)
and fill down.

Then to get the last occurrence of a row with "Class" above the current row - let's say above A351, just use
=max(B$1,B350).

and the number of rows between the 2 occurrences (the current row and the previous row with "Class") is just
=Row() - max(B$1,B350)


The alternative to allow for this to be more dynamic (the values in A246 and A351 can change) would take a little more work.

Fred


This Site

Got a version of Excel that uses the menu interface (Excel 97, Excel 2000, Excel 2002, or Excel 2003)? This site is for you! If you use a later version of Excel, visit our ExcelTips site focusing on the ribbon interface.

Newest Tips
Subscribe

FREE SERVICE: Get tips like this every week in ExcelTips, a free productivity newsletter. Enter your address and click "Subscribe."

(Your e-mail address is not shared with anyone, ever.)

View the most recent newsletter.