Sum every 11 rows excel - excel

Question

I have a table with 2600+ rows, related to towns in my region and their population; each town has 11 rows, one for each age class (0-9, 10-19, and so on).
I need to get the sum of the population of each town; of course I can do it manually but it's a never ending job; I wonder if there's some kind of command that tells excel to do the sum every 11 rows and do it for all the towns.
I think it's a kind of loop but I have no idea about how to do it.

Answer 1

The problem can be reduced by using the SUMIF function. The question then becomes how to apply this to your dataset.
Assuming one of the columns in your 2600+ rows contains the town name (or another unique identifier), and you have a list of towns (or other unique identifier), the below method can be used.
The formula in E2 is =SUMIF(A:A,D2,C:C), and in E3 =SUMIF(A:A,D3,C:C). A to C is the list of all data, D is a list of towns.

Answer 2

For a VBA solution, you should be able to use a step in the loop.
So if you wish to step by 11 rows at a time.
Public Sub IterateRows()
Dim rData As Range, rPtr As Range
Dim dSum As Double
Dim i As long
Set rData = Sheet1.Range("A1:A1000")
For i = 1 To rData.Rows.Count Step 11
Set rPtr = rData(1).Resize(11).Offset(i - 1)
dSum = Application.WorksheetFunction.Sum(rPtr)
Next
End Sub
If you want a worksheet function solution, you will probably have to use the MOD operator and check for when the value is zero..

Answer 3

You can also try this manual method which is not a never ending job; i.e.:
in E11 put your formula as =SUM(C1:C11)
copy range E1:E11
select range E12:E2600 and paste special function

Answer 4

Do you have any reference columns? As in...say for example Column A has the Town Name, and Column B has the Age Class, and Column C has the values.
Going down the rows Column A will have repeating town names, yes?
Like this:
Town - Age Class - Pop
Wherever - 0-9 - 1000
Wherever - 10-19 - 2000
Wheverer - 20-29 - 2500
Assuming you have maintained the data structure (NO GAPS) a possible solution in Column D (or whatever column just make sure you change the references) could be (putting this in D2 and dragging it down the length of your sheet):
=IF(A1<>A2,SUM(INDIRECT("C"&ROW(A2)&":C"&SUMPRODUCT(MAX((A:A=A2)*(ROW(A:A)))))),D1)
This works if you have any amount of rows per town, so long as you SORT by town name so the same names are next to each other in the list and there are no gaps.
In the above test data set I subtracted 250 from each Values count per Town going down (each class has 250 less than the previous city) just to show some variation in the output...you can see each city has 2750 (250 * 11) less pop than the previous.
Basically it builds an array with a starting position of "not the town above" in the first row it encounters a new town name to an ending position of "last (max) position of new town in same list" so that is how it doesn't matter how many rows you have per town. From 1 to memory limit basically, I think. :)
ALTHOUGH, this also works:
=SUMIF(A:A,A2,C:C)
Yep. Not kidding just drag that down Column D...

Answer 5

Assuming the following structure
This is a very easy task using a pivot table.
For LibreOffice Calc:
Just select the complete data area including the column headers (in my example: A1:C13);
Menu Data -> Pivot Table;
Current selection;
Following settings for Pivot table:
(drag the Town field into the Row Fiels area, and the Count field into the Data fields area. LO Calc will offer to calculate the Sum of the count entries by default).
Hit OK - the resulting pivot table will look like this:
This solution has the advantage that the source data area hasn't to be sorted by town, and it doesn't matter if some towns don't have nine value rows each. Additionally, you don't need any formulas.
EDIT:
You can work with the contents of the pivot table the same way as with calculated results. For example, you could use the pivot table values to calculate the sum for some of the towns (in my example, calculate the sum for town B and C based on the pivot table values B3 and B4 respectively):

Answer 6

You could do this with the MOD function, which gives the remainder of division. You could look at each row number and if its MOD of 11 equals zero, then it's the row you're looking for.
I am counting 10 items in each section in your example so I'm not sure I completely understand. Let's assume you need to sum every row that ends in a 9 (A9, A19, A29, etc.). You can replace the 9's below with an 11.
=ROW(A9) gets you the row number.
=MOD(ROW(A9),9) gets you a TRUE or false on weather that number is divisible by 9. If it is a multiple of 9, it will return the number 0.
Now use the SUM function and hit CONTROL+SHIFT+ENTER to complete it. Note that the formula bar indicates that this is an array function by using curly braces. You don't need to type those in yourself.
{=SUM(A1:A9*(MOD(ROW(A1:A9),9)=0))}