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.
9 Responses to “CP044: My first dashboard was a failure!!!”
CONGRATS on the book!
Thanks for this podcast. It's great to hear about your disaster and recovery. It's a reminder that we're all human. None of this skill came easily.
Thank you Oz. I believe that we learn most by analyzing our mistakes.
Hey chandoo
this really a good lesson learned
but as I have already stated in one of my previous email that it would be more helpful for us if you could release videos of your classes for us
thanks
The article gave me motivation, especially you describing the terrible disaster that you faced but how to get back from the setbacks. Thanks for that, but with video this will be more fun.
Hi Nafi,
Thanks for your comments. Please note that this is (and will be) audio podcast. For videos, I suggest subscribing to our YouTube channel. No point listening to audio and saying its not video.
You always motivate me with respect of the tools in excel. How we can really exploit it to the fullest. Thanks very much
Thank you Amankwah... 🙂
Thank you very much, Chandoo, for your excellent lessons, I am anxious to learn so valuable tips and tricks from you, keep up the great job!
I truly appreciate the transcripts of the podcasts, because as a speaker of English as a second language, it allows me to fully understand the material. It'd be great if you can add transcripts to your online courses too, I am sure people will welcome this feature.
Dashboards for Excel has arrived in Laguna Beach, CA! Thanks!
Now I need to make time to "learn and inwardly digest" its contents as one of my high school teachers would admonish us!