What is a time stamp?
Often when you use excel to track a particular item (like expenses, exercise schedules, investments) you usually enter the current date (and time). This is nothing but timestamping. Once the item is time stamped, it is much more easier to analyze it.
So how do I generate timestamps in Excel?
We all know about the now() formula in excel and how it tells you the current date and time. The only problem with it is that, when you press F9 or recalculate formulas, the now() will be changed to reflect latest date and time. Thus we cannot use NOW() as a time stamp.
A good alternative (although manual) is to use keyboard shortcuts CTRL + ; or CTRL + : to insert current date and time in the active cell. Since this places the value, we don’t need to worry even if the date or time changes. But the only issue is, every time you need a time stamp you have to press the 2 keys.
A better way to get timestamps in excel is to use a special type of formulas, called as circular formulas.
What the heck is a circular formula?
A circular formula refers to itself (or to another cell which in turn refers to this cell). Confused ? Well, let me give you an example.
=if(A2<1000, A2+1,A2)
Now the above formula is normal, but the moment you write it in the cell A2, you have made it a circular formula. So, each time you run the formula (by pressing F9) the value in A2 will go up by 1, just like an incrementing counter.
But here is a thing you should be aware of: There is a setting called “iterations”, it tells excel how many times it should run a formula before finalizing the result.
This setting wouldn’t make any sense in case of regular formulas. But it is very important for circular formulas. If not for this, excel would go in to an infinite loop and stall.
Now, by default iterations in formula computation is turned off. That means when you write a circular formula or create a circular reference, excel shows you a message warning you and it doesn’t evaluate the formula.To turn the iterative calculation, and thus enable usage of circular formulas, go to menu > tools > options > calculation tab and check the iteration box. In excel 2007, you can go to office button > excel options > formulas > iteration area.
As you can see the default max. iterations per formula execution is 100, which means, every time you run the circular formula, excel calculates it 100 times before presenting the value. So our formula =if(A2<1000, A2+1,A2) written in cell A2 would go up by 100 every time you run.
Back to Generating Time Stamps
Now that you are knowledgeable about circular formulas, here is how we can refine the “time stamp generation” problem:
if the cell doesn’t already have time stamp, insert current date time using now(), otherwise leave the value as it is
and we will trigger the formula once we make certain changes, for eg. whenever you enter data, you can tell excel enter timestamps. See this:
The formula itself is very simple:
=IF(C3<>"",IF(B3="",NOW(),B3),"") in cell B3.
What it does?
It checks cell C3 and whenever it is not empty it runs the circular formula IF(B3="",NOW(),B3) which fetches NOW() value only if the cell B3 doesn’t already have a value, thus serving timestamps.
The above formula works only if you have enabled iterative calculation mode as described above.
Your thoughts ?
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12 Responses to “Analyzing Search Keywords using Excel : Array Formulas in Real Life”
Very interesting Chandoo, as always. Personally I find endless uses for formulae such as {=sum(if(B$2:B$5=$A2,$C$2$C$5))}, just the flexibility in absolute and relative relative referencing and multiple conditions gives it the edge over dsum and others methods.
I've added to my blog a piece on SQL in VBA that I think might be of interest to you http://aviatormonkey.wordpress.com/2009/02/10/lesson-one-sql-in-vba/ . It's a bit techie, but I think you might like it.
Keep up the good work, aviatormonkey
Hi Chandoo,
You might find this coded solution I posted on a forum interesting.
http://www.excelforum.com/excel-programming/680810-create-tag-cloud-in-vba-possible.html
[...] under certain circumstances. One of the tips involved arranging search keywords in excel using Array Forumlas. Basically, if you need to know how frequent a word or group of keywords appear, you can use this [...]
@Aviatormonkey: Thanks for sharing the url. I found it a bit technical.. but very interesting.
@Andy: Looks like Jarad, the person who emailed me this problem has posted the same in excelforum too. Very good solution btw...
Realy great article
"You can take this basic model and extend it to include parameters like number of searches each key phrase has, how long the users stay on the site etc. to enhance the way tag cloud is generated and colored."
How would you go about doing this? I think it would need some VB
Hi,
I found the usage very interesting, but is giving me hard time because the LENs formula that use ranges are not considering the full range, in other words, the LEN formula is only bringing results from the respective "line" cell.
Using the example, when I place the formula to calculate the frequency for "windows" brings me only 1 result, not 11 as displayed in the example. It seems that the LEN formula using ranges is considering the respective line within the range, not the full range.
Any hint?
@Thiago
You have to enter the formula as an Array Formula
Enter the Formula and press Ctrl+Shift+Enter
Not just Enter
Thank you, Hui! I couldn't work out how this didn't work
is there a limit to the number of lines it can analyse.
Ie i am trying to get this to work on a list of sentances 1500 long.
@Gary
In Excel 2010/2013 Excel is only limited by available memory,
So just give it a go
As always try on a copy of the file first if you have any doubts
Apologies if I am missing something, but coudn't getting frequency be easier with Countif formula. Something like this - COUNTIF(Range with text,"*"&_cell with keyword_&"*")
Apologies if I missed, but what is the Array Formula to:
1. Analyze a list of URL's or a list of word phrases to understand frequency;
2. List in a nearby column from most used words to least used words;
3. Next to the list of words the count of occurrences.