While preparing a project plan, I had a strange problem. I wanted to highlight all the project tasks that fall with-in a certain date range. At the lowest level, the problem is like this:
There are 2 ranges of dates (a,b) and (x,y) and I want to know if they overlap (ie at least one date common between a,b and x,y)
The formula for testing such a thing seemed tricky at first. So I drew the conditions on paper to get clarity on what we should test. Evidently, there are 4 ways in dates (a,b) can overlap with dates (x,y) as shown below:
Now, we can test for the overlap condition using a formula like this:
If x is between a and b
or a is between x and y
then overlap
else do not overlap
As you know, there is no formula in excel like isbetween(). So we have to break it up to 2 conditions and an AND() Formula. Finally the formula becomes,
=if(or(and(x>=a,x<=b),and(a>=x,a<=y)),"Overlap","Do not overlap")
Now, it seemed like quite a big formula for testing if 2 ranges of dates overlap.
So, I continued my quest for even shorter formula.
After sometime, I realized that if we test for non-overlap instead of overlap, we can write a shorter formula.
Do not understand? Let me explain.
While there are 4 ways in which (a,b) can overlap with (x,y), there are only two ways in which (a,b) cannot overlap with (x,y). See this to understand:
Now, testing above conditions is very straight forward in excel.
the formula becomes, =if(or(y<a,b<x),"Do not overlap","Overlap")
The formula is much shorter and easy to maintain.
I was able to use it to test if a set of tasks in the project plan are running between given dates (for eg. next week). All is well in the end.
How do you test overlap conditions?
Do you ever have to test overlap conditions? What kind of formulas have you used? Please share your formula tips & tricks using comments.
15 Responses to “Christmas Gift List – Set your budget and track gifts using Excel”
[...] Christmas Gift List – Set your budget and track gifts using Excel … [...]
I'm confused: if you spend $10, and your budget is $40, shouldn't the amount in the "Within Budget?" column stay black, since you didn't go over budget?
In other words, since we overspent on the electronic photo frame, shouldn't the $8 cell turn red?
@JP.. maybe Steven is encouraging consumerism... ?
I havent realized it earlier, but now I see it. If you unprotect the sheet, you can change the formula in Column I to =IF(G13=0;" ";F13-G13) from =IF(G13=0;" ";G13-F13), that should correct the behavior.
Thanks Chandoo. I thought of making a shopping list spreadsheet for Christmas, but this is neat so I think I'll use this instead.
Chandoo & Steven thanks for this spreadsheet. But for the sake of a person who has been staring at this megaformula in vain for the last 40 mins and not afraid to ask, would it be possible for you to walk us through the logic used here?
=SUM(SUMPRODUCT(SUBTOTAL(3,OFFSET($K$13:$K$62,ROW($K$13:$K$62)-MIN(ROW($K$13:$K$62)),0,1)),--($K$13:$K$62="-"))+SUMPRODUCT(SUBTOTAL(3,OFFSET($K$13:$K$62,ROW($K$13:$K$62)-MIN(ROW($K$13:$K$62)),0,1)),--($K$13:$K$62="0")))&" / "&SUBTOTAL(2,$G$13:$G$62)
Thanks Chandoo.. This is one of the best budget spreadsheets I've ever seen.. The Arrays are out of this world!! And it's FREE!!
Chandoo, can you tell us more about Steven? Does he have his own site?
JP, I think Chandoo changed it when he changed the currency formatting from £ to $, a negative figure is a good thing in this case. But don't change the formulas, the overbudget and under budget won't work properly if you do. Also Chandoo I think you've accidentally broke the conditional formatting for the alternating row colouring the formula is different to the version I sent you. As for the megaformula chrisham, it gave me a headache trying to get it all working, so I will let Chandoo talk you through it.
Hi,
In cells I6 and I7, I understand that subtotal together with offset function returns an array of ones after which, the sumproduct function gives the desired result.
But I’m not able to figure out the reason for using an array in I8 to return the most expensive gift.
Can’t the formula be just
“=VLOOKUP(SUBTOTAL(4,$G$13:$G$62),$G$13:$J$62,4,0)”
Savithri, Cell I8 needs the array, if the formula was “=VLOOKUP(SUBTOTAL(4,$G$13:$G$62),$G$13:$J$62,4,0)” it would find the highest price from the filtered range (i.e. highest actual in filtered range is $50) BUT then return the first person with that actual, not looking in just the filtered range (so first person on the list with a $50 actual.)
To see what I mean, change the formula, then change all the actuals to $50 then filter for baby, it lists the first name on the list.
But a good question 🙂
Thank you. I now realise that the array is used to get the ‘filtered range’ instead of the entire range, as table array for look up value.
[...] Download This Template [...]
this looks like an awesome excel sheet!! is there anyway i can get it emailed to me unprotected? for some reason, i am unable to download it 🙁 help!!
Hi I also can not download to a mac as the sheet is protected any help would be great
[...] to send her a pricey present. Rather, send a card with a picture of your child. Here’s a cool Excel sheet that will help you estimate your budget per person and let you track [...]
[...] husband and I pour/poor over the Christmas spreadsheet (yes, I do know how dorky that sounds, but we’re not the only ones!), figuring out who should give what to whom. We live at a distance from most of our family, so it [...]