Are you tired of manually calculating the sum of column B every time there’s a change in value in column A in your Google Sheets? Well, worry no more! I’m here to share with you not one, but two incredible array formulas that will automate this task for you.
The Regular Array Formula to Sum Column B When Value in Column A Changes
Let’s start with the first formula, shall we? This formula, when entered in cell C2, will calculate the sum of cells in column B until a change in value occurs in column A. And the best part? It covers the entire columns A and B automatically!
Here’s the master formula you need to enter:
=iferror(ArrayFormula(vlookup(row(A2:A),{if(len(A2:A),lookup(unique(A2:A),A2:A,row(A2:A))),if(len(A2:A),sumif(A2:A,unique(A2:A),B2:B))},2,0)))This formula uses a combination of array formulas and the Vlookup function to achieve the desired result. The search_key argument, which is row(A2:A), returns the row numbers in sequential order. The range argument, underlined in red and green colors, forms a two-column range that takes into account any changes in column A values. Finally, the index argument specifies the column number in the range, which in this case is 2 (column B).
But what if you want to use different columns other than A and B? Don’t worry, it’s still possible! Just ensure that you adjust the formula accordingly. For example, if your range for column A is A5:A and the range for column B is B5:B, you should change the formula row(A2:A) to row(A5:A).
Formula Explanation
Rather than diving into a detailed breakdown of the formula, I’ll give you a brief overview of its logic. Please note that it’s not necessary to follow this logic, but it might help you understand how the formula works.
The master formula is essentially a Vlookup formula that combines two separate formulas: one that returns the row number of value changes in column A, and another that calculates the sum based on those changes. The search_key argument, row(A2:A), acts as the reference for the Vlookup. The range argument consists of the formulas highlighted in red and green, which return the row numbers and sum values, respectively. Finally, the index argument specifies that the sum values should be returned (column 2 in the range).
And there you have it! With this array formula, you can effortlessly sum column B whenever there’s a change in column A values in Google Sheets.
The Lambda Solution to Sum Column B When Value Changes in Column A
If you’re looking for an alternative to the regular array formula, I’ve got you covered! Introducing the lambda-based solution, a somewhat easier formula that accomplishes the same result.
Here’s the master formula you need to enter:
=ArrayFormula(ifna(lambda(x,y,byrow(x,lambda(r,if(row(r)=xmatch(r,x,0,-1)+1, sum(filter(y,x=r)),))))(A2:A,B2:B)))This lambda formula works by filtering column B based on the criterion in column A (A2, A3, A4, and so on), and then using the SUM function to calculate the total. The XMATCH function is used to find the last row of the search criterion in column A. With the help of the IF function, the total value is placed in the corresponding row. The BYROW function repeats this process for each criterion in the FILTER. And the LAMBDA function? It simply shortens the formula and makes it more concise.
So there you have it, my friend! Two amazing array formulas that will make your life easier when it comes to summing column B in Google Sheets. Say goodbye to manual calculations and hello to automated simplicity!
Oh, and if you want to learn more cool tips and tricks for Google Sheets, make sure to check out Crawlan.com for all your spreadsheet needs.
Happy summing!
