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.
8 Responses to “Introducing PHD Sparkline Maker – Dead Simple way to Create Excel Sparklines”
This looks like it could be very useful for a project I'm putting together right now, thank you so much. Quick & silly question, how do I copy & paste the sparkline as a picture?
Question answered. For anyone else:
Select chart>Hold Shift key & select Edit/Copy Picture>Paste
[...] more information about PHD Sparkline Maker, please read this article and to learn more about Sparklines, read this article from Microsoft Excel 2010 blog. Also there [...]
Am I right in thinking that the y-axis is set automatically by excel?
That makes it possible to get the column chart not to start at zero.
Andy - yes, it is currently set to 'auto', which defaults to a zero base for positive values, but you can change that by left-clicking the chart, then choosing (in Excel 2007):
"Chart Tools/Layout/Axes/Primary Vertical Axis/More Primary Vertical Axis Options"
PUBLIC SERVICE ANNOUNCEMENT: When manually editing a chart's minimum/maximum axis values, PLEASE be sure there's a valid reason and that doing so won't skew the message shown by the data (e.g. by exaggerating differences). If in doubt, go back and read Tufte. (W.W.T.D.?)
[...] gridlines, axis, legend, titles, labels etc.) and resize it so that it fits nicely in a cell [example]. This is the easiest and cleanest way to get sparklines in earlier versions of excel. However this [...]
thanks for the work creating the template!!!!
looks good