As mentioned earlier, I have conducted a small interview with Charley Kyd – an Excel MVP, author of four books and 50+ articles for various national media, owner of exceluser.com and creator of popular products like plug-n-play excel dashboard kit. He sent me the answers almost a week back, but I could push the interview only today due to my travel and settling down stuff. As expected the interview is very entertaining and useful. I hope you like this.
Q: What are your 3 favorite formulas?
I don’t have favorite formulas, but here are three functions I use all the time:
- INDEX
- MATCH (with the third argument equal to zero)
- SUMPRODUCT
Q: If I am an excel newbie, what three books or resources you would recommend?
MrExcel.com forum for asking questions
Check out Microsoft discussion groups and microsoft.public.excel newsgroup for asking questions
Q: How can managers and analysts be more productive in using excel?
- Don’t upgrade to Excel 2007, or, if you do, keep a copy of Excel 2003 on your computer. (When you install 2007 on top of 2003, answer No when the install program asks if you want to upgrade to the new version.)
- Wherever possible, separate your data from your presentation, then use formulas to pull your data into your presentation. (My three “favorite” functions help you to do that.)
- Learn shortcut keys. In versions prior to Excel 2007, the Alt key commands are consistent. And 2007, allows you to use the earlier versions’ Alt-key combinations for many things.
Q: What resources (books, websites) would you recommend for this type of people?
I’ll be talking more about separating data and presentation at ExcelUser.com over the coming year. Subscribe to my newsletter to be alerted about developments.
Q: Do you think a small business owner run her shop using excel and few free tools ? What you suggest her?
Yes and no. I would not recommend that you use Excel for accounting. Quicken is really inexpensive and does a much better job. But Excel can help in many other ways, including analysis, forecasting, pricing, and so on.
Q: Where do you think most of us waste a lot of time while using excel ?
- Importing data from other systems / sources?
We perform the same reporting or analytical task over and over again, but with different data. When you notice yourself doing this, try to come up with ways that you can use formulas in one workbook to pull the data you need from a data workbook. That way, you can merely point your analysis or presentation to an updated data workbook without having to do everything over again from scratch.
- Formulas and errors ?
Many people don’t know how to switch to manual calculation. (Tools, Options, Calculation, Manual.) This allows us to work on a big spreadsheet without waiting for it to calculate all the time. Then, when we want to calculate, we merely press the F9 key.Many people create much larger workbooks and spreadsheets than they should, and then get lost in them. I try to keep my workbooks and spreadsheets small, unless I have a specific reason not to do so.
Many people create many links between workbooks. This is a problem because the links can break, or get broken, or generate circular calculation errors. I try to link only from data to presentation.
Assume we have a column of data in the range A5:A10. If we want to sum that data, people generally enter the formula =SUM(A5:A10). Instead, I format cells A4 and A11 with a full border and gray fill. Then I sum using the range A4:A11. This allows me to add or delete rows between the gray borders without having to worry about formulas that reference that data. As long as I don’t touch the two gray border rows, I know I’m safe. (I don’t use this approach if I’m going to print the page for others, because it looks ugly. But that’s not a problem most of the time.)
- Formatting ?
I try never to use Merge Cells for centering labels across several columns. (In fact, I doubt that I’ve used Merge Cells more than half a dozen times, *ever*.) Instead, I use Format, Cells, Alignment, Horizontal, Center Across Selection. This achieves the same results but without my having to deal with the problems that merged cells creates.
- VBA ? VBA is very powerful, and can be a lot of fun. But be careful, it can grow to be an addiction. Most VBA users have found themselves spending hours to write a program that saves them several minutes. That’s obviously not a good use of our time.I try very hard to comment my code heavily. And when I look at old code, I *always* wish that I had commented it even more heavily. When you’re in the middle of a project, the reason for each line of code is obvious. But six months later, the whole thing is a mystery. COMMENT YOUR CODE.
Q: What is the best way for a non-programmer to learn and use VBA in her day to day work?
- Stay with a version of Excel prior to 2007, for two reasons: There aren’t any good macro books about 2007, and the macro recorder doesn’t work for a lot of what you do in 2007.
- Get a beginners book and start to experiment.
- Use the macro recorder and look at the results.
- Ask questions in newsgroups and forums.
- Get to know the Object Browser. (In the VBE, choose View, Object Browser. Or merely press the F2 key.)
I am very thankful to Charley for agreeing for this interview and sharing his views on some of the day to day excel issues all of us face. Many thanks to commenters who suggested some of the questions. I hope you found this interview helpful. Let me know through comments or email what you think about this.
Also share your ideas on who else should be interviewed?
14 Responses to “How many ‘Friday the 13th’s are in this year? [Formula fun + challenge]”
in C3=2016
in C4=3
in C5=1 (the first next year with three Friday the 13ths)
=SMALL(IF(MMULT(--(MOD(DATE(C3+ROW(1:1000),COLUMN(A:L),13),7)=6),ROW(1:12)^0)=C4,C3+ROW(1:1000)),C5)
formula check in the next 1000 years
This will generate a table of counts of Friday the 13th's by year. If I didn't screw it up the next year with three is 2026.
I created a simple parameter table with a start date and end date that I wanted to evaluate. That calculates the number of days and generates a list of those days. Then filter and group. The generation of the list in power query (i.e. without populating a date table in excel) is pretty cool, otherwise this isn't really doing anything than creating a big date and filtering/counting.
let
Source = List.Dates(StartDateAsDate, Days2, #duration(1,0,0,0)),
ConvertDateListToTable = Table.FromList(Source, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
AddDayOfMonthColumn = Table.AddColumn(ConvertDateListToTable, "DayOfMonth", each Date.Day([Column1])),
AddYearColumn = Table.AddColumn(AddDayOfMonthColumn, "Year", each Date.Year([Column1])),
AddDayOfWeekColumn = Table.AddColumn(AddYearColumn, "Day of Week", each Date.DayOfWeek([Column1])),
FilterFriday13 = Table.SelectRows(AddDayOfWeekColumn, each ([DayOfMonth] = 13) and ([Day of Week] = 5)),
Friday13thsByYear = Table.Group(FilterFriday13, {"Year"}, {{"Number of Friday the 13ths!", each Table.RowCount(_), type number}})
in
Friday13thsByYear
With the parameters replaced by values should you want to play along at home. This runs for 20 years starting on 1/1/2016.
let
Source = List.Dates(#date(2016,1,1), 7300, #duration(1,0,0,0)),
ConvertDateListToTable = Table.FromList(Source, Splitter.SplitByNothing(), null, null, ExtraValues.Error),
AddDayOfMonthColumn = Table.AddColumn(ConvertDateListToTable, "DayOfMonth", each Date.Day([Column1])),
AddYearColumn = Table.AddColumn(AddDayOfMonthColumn, "Year", each Date.Year([Column1])),
AddDayOfWeekColumn = Table.AddColumn(AddYearColumn, "Day of Week", each Date.DayOfWeek([Column1])),
FilterFriday13 = Table.SelectRows(AddDayOfWeekColumn, each ([DayOfMonth] = 13) and ([Day of Week] = 5)),
Friday13thsByYear = Table.Group(FilterFriday13, {"Year"}, {{"Number of Friday the 13ths!", each Table.RowCount(_), type number}})
in
Friday13thsByYear
=MATCH(3,MMULT(N(WEEKDAY(DATE(C3+ROW(1:100)-1,COLUMN(A:L),13))=6),1^ROW(1:12)),)+C3-1
It should be pointed out that Alex's solution, unlike some others, has the additional advantage of being non-array. My solution was nearly identical but with -- and SIGN instead of N and 1^.
=C3-1+MATCH(3,MMULT(--(WEEKDAY(DATE(C3-1+ROW(1:25),COLUMN(A:L),13))=6),SIGN(ROW(1:12))),0)
Sub Friday13()
Dim StartDate As Date
Dim EndDate As Date
Dim x As Long
Dim r As Long
Range("C7:C12").ClearContents
StartDate = CDate("01/01/" & Range("C3"))
EndDate = CDate("31/12/" & Range("C3"))
r = 7
For x = StartDate To EndDate
If Day(x) = 13 And Weekday(x, vbMonday) = 5 Then
Cells(r, 3) = Month(x)
r = r + 1
End If
Next
End Sub
Calculate next year with 3 Friday 13th. Good for 100 years different from year entered in cell C3
Sub ThreeFriday13()
Dim StartDate As Date
Dim EndDate As Date
Dim x As Long
Dim WhatYear As Integer
Dim Counter As Integer
Range("E7").ClearContents
StartDate = CDate("01/01/" & Range("C3") + 1)
EndDate = CDate("31/12/" & Range("C3") + 100)
Counter = 0
For x = StartDate To EndDate
If WhatYear Year(x) Then
WhatYear = Year(x)
'Different year so reset counter
Counter = 0
End If
If Day(x) = 13 And Weekday(x, vbMonday) = 5 Then
Counter = Counter + 1
If Counter = 3 Then
WhatYear = Year(x)
Exit For
End If
End If
Next
Range("E7") = WhatYear
End Sub
*RE-POST as not equal did not show earliuer
Calculate next year with 3 Friday 13th. Good for 100 years different from year entered in cell C3
Sub ThreeFriday13()
Dim StartDate As Date
Dim EndDate As Date
Dim x As Long
Dim WhatYear As Integer
Dim Counter As Integer
Range("E7").ClearContents
StartDate = CDate("01/01/" & Range("C3") + 1)
EndDate = CDate("31/12/" & Range("C3") + 100)
Counter = 0
For x = StartDate To EndDate
If WhatYear NE Year(x) Then
WhatYear = Year(x)
'Different year so reset counter
Counter = 0
End If
If Day(x) = 13 And Weekday(x, vbMonday) = 5 Then
Counter = Counter + 1
If Counter = 3 Then
WhatYear = Year(x)
Exit For
End If
End If
Next
Range("E7") = WhatYear
End Sub
earlier*
I've a doubt with using array formula here.
In sample workbook, I tried to replicate the formula again.
=IFERROR(SMALL(IF(WEEKDAY(DATE($C$3,ROW($A$1:$A$12),13))=6,ROW($A$1:$A$12)),$B7),"")
For this I selected C7 to C12, and typed the same formula and pressed ctrl+alt+Enter. But in all cells it is taking $B7 (and not $B7, $B8, $B9.... etc)
and since it is array formula I can't edit individual cell.
Please guide.
Thanks
Hi Chandoo,
Cool stuff. You need to clarify that the answer of 5 represents the 1st month in the year that has a Friday the 13th, and not the number of Fridays the 13th in the year. Subtle, but important difference.
Thanks,
Pablo
I like the MMULT() function far more, but here's how I would have tackled it. It uses an EDATE() base and MODE() over 100 years. I'm assuming that 100 years is enough time to catch the next year with 3 friday 13th's. Array entered, of course.
{=MODE(IFERROR(YEAR(IF((WEEKDAY(EDATE(DATE(C3, 1, 13), ROW(INDIRECT("1:1200"))))=6), EDATE(DATE(C3, 1, 13), ROW(INDIRECT("1:1200"))), "")), ""))}
Finding all the Friday the 13ths in a Year:
=SUMPRODUCT((DAY(ROW(INDIRECT(DATE(C3,1,1)&":"&DATE(C3,12,31))))=13)*(TEXT(ROW(INDIRECT(DATE(C3,1,1)&":"&DATE(C3,12,31))),"ddd")="Fri"))
{=sum(if(day.of.week(DATe($YEAR;{1;2;3;4;5;6;7;8;9;10;11;12};13);1)=6;1;0))}
just list the years