Last week in the Chandoo.org Forums a user asked a question
“How do I convert a Roman Numeral to a Number eg: MMMCCCLVII to 3357”
User Xlstime presented the solution of:
=MATCH(A2,INDEX(ROMAN(ROW(INDIRECT(“1:3999”))),0),0)
Today we are going to look at how and why that simple formula works
As always at Formula Forensics you can follow along using a sample file: Download Sample File
Solution
Excel has a Roman function wherein =Roman(3357, 0) will return MMMCCCLVII
I knew there was no such reverse Roman function prior to Excel 2013 and so my initial thought was to look at a VBA Solution.
See notes on the Arabic Excel function at the end of the post.
However Xlstime presented =MATCH(A2,INDEX(ROMAN(ROW(INDIRECT(“1:3999”))),0),0)
How does this work?
lets start by pulling it apart from the inside out
=MATCH(A2,INDEX(ROMAN(ROW(INDIRECT(“1:3999”))),0),0)
The Indirect Function simply takes its inputs and converts them to a Range, in this case 1:3999.
We will study why 3999 later
=MATCH(A2,INDEX(ROMAN(ROW(INDIRECT(“1:3999”))),0),0)
The next function working out is Row()
Excel will convert the function ROW(INDIRECT(“1:3999”)) to an array of Row Numbers
={1;2;3;4;5;6;7;8;9;10;11; …. 3995;3996;3997;3998;3999}
You can see this if you goto cell D7 in the Sample File, press F2 and then F9
I limited the numbers to 300 as Excel cannot display more than 8,192 digits
Stepping out one more function:
=MATCH(A2,INDEX(ROMAN(ROW(INDIRECT(“1:3999”))),0),0)
The Roman() function converts its inputs into Roman Numbers
eg: Roman(58) will return LVIII
But as we are feeding it an array of numbers from 1 to 3999 Excel handles all these and converts them to an Array of Roman Numbers
Goto D9 in the sample file =ROMAN(ROW(INDIRECT(“1:300”))) press F2 and then F9
Excel returns an array of roman numbers
={“I”;”II”;”III”;”IV”;”V”;”VI”;”VII”;”VIII”; … “CCXCVI”;”CCXCVII”;”CCXCVIII”;”CCXCIX”;”CCC”}
We have limited the example to 300 as Excel cannot display more than 8,192 characters when processing a Function using F9.
Stepping out one more function
=MATCH(A2,INDEX(ROMAN(ROW(INDIRECT(“1:3999”))),0),0)
The Excel Index() function is taking the Array of Roman Numerals and Converting it into a single Column array
This isn’t technically needed but it simplifies the solution
If you goto cell D11 in the sample file =INDEX(ROMAN(ROW(INDIRECT(“1:3999”))),0) press F2 and then F9
Excel returns an array of roman numbers
={“I”;”II”;”III”;”IV”;”V”;”VI”;”VII”;”VIII”; … “CCXCVI”;”CCXCVII”;”CCXCVIII”;”CCXCIX”;”CCC”}
This is exactly the same as the previous output from the Roman() function above, Except that it is now a Single Vertical Array. This is important for the next function.
Stepping out one more function
=MATCH(A2,INDEX(ROMAN(ROW(INDIRECT(“1:3999”))),0),0)
We can see here that the Array of Roman Numerals is now being fed into a Match() function.
Match uses the Syntax =Match(Lookup value, Lookup Array, Match Type)
Match returns the position of the Lookup value within the array
So in our example
The Lookup value is A2 or our Roman Numeral MMMCCCLVII
The Lookup Array is an array of Roman Numerals from 1 to 3999
={“I”;”II”;”III”;”IV”;”V”;”VI”;”VII”;”VIII”; … “MMMCMXCV”; “MMMCMXCVI”; “MMMCMXCVII”; “MMMCMXCVIII”; “MMMCMXCIX”}
and the Match Type is 0 or an exact Match
So the Match function will lookup the value MMMCCCLVII in the array and find it in position number 3357, which happens to correspond to the Number of the Roman Numeral and Return 3357 as the result.
Why are we limited to 3999 numbers.
The Excel Roman() function is limited to numbers up to 3999
Why 3999?
Because in Roman Numerals there is no Letter for 5,000 and 4,000 would be shown as M before the Letter for 5,000.
Why did we need the Index() function?
If you goto D17 in the sample file you will see the formula:
=MATCH(A2,ROMAN(ROW(INDIRECT(“1:3999”))),0)
It is the same formula as above but without the Index() function
You will see that it is returning a #VALUE! error
If you edit the formula with F2 and then press F9 to process the function you will see it now shows 3357
What s happening here?
Pressing F9 is the same as Array Entering the Function
so if you edit the function pressing F2 and now Array Enter the function by pressing Ctrl+Shift+Enter, excel now returns 3357
The Index() function puts a wrapper around the array for processing by the Match() function and so Array Entering is avoided.
Most array formulas that require Ctrl+Shift+Enter can be rewritten incorporating an INDEX wrapper and will not require the Ctrl+Shift+Enter confirmation.
The Excel Arabic Function
In 2013, Microsoft introduced the Arabic function to Excel
To use simply use =Arabic(A2) or =Arabic(“MMMCCCLVII”)
You can read about the Syntax of the function in the Excel Help.
Download
You can download a copy of the above file and follow along, Download Sample File.
A Challenge
Can you solve the problem another way ?
Post your solutions in the comments below.
Other Posts in this Series
The Formula Forensics Series contains a wealth of useful solutions and information specifically about how Normal Formula and specifically Array Formula work.
You can learn more about how to pull Excel Formulas apart in the following posts: http://chandoo.org/wp/formula-forensics-homepage/
If you have a formula and you want to understand how it works contact Hui and it may be featured in future posts.
25 Responses to “Display Alerts in Dashboards to Grab User Attention [Quick Tip]”
I prefer the red,grey,light grey,black icon set. I've also used in-cell pie charts from Fabrice's Sparklines for Excel as an alert which could also provide another piece of information.
I prefer the red,grey,light grey,black icon set. I've also used in-cell pie charts from Fabrice's Sparklines for Excel as an alert which can also provide another piece of information.
For Excel 2007, your formula should do the same as the Excel 2003 version, so that non-alert rows are blank - if they are 0, the unnecessary green icon will show
Hi Chandoo,
Nice Post !! just to add something for EXL 2003, we can also 4 Ifs and link to the alert data
For Ex: If we have alert data in Cell A2 and want to split in 4 orders namely <25%, 25-50%, 50-75% and 75%< then we can following formula and put fonts as you have suggested :
=IF(A2<0.25,CHAR(153),IF(A2<=0.5,CHAR(155),IF(A2=0.76,CHAR(152)))))
And then using Conditional Formating we can dashboard reflected on different COLOURS as per their respective alert.
Best Regards
Rohit1409
Hi Chandoo,
Nice Post !!! just to add something for EXL 2003, we can also 4 Ifs and link to the alert data
For Ex: If we have alert data in Cell A2 and want to split in 4 orders namely <25%, 25-50%, 50-75% and 75%< then we can following formula and put fonts as you have suggested :
=IF(A2<0.25,CHAR(153),IF(A2<=0.5,CHAR(155),IF(A2=0.76,CHAR(152)))))
And then using Conditional Formating we can dashboard reflected on different COLOURS as per their respective alert.
Best Regards
Rohit1409
The Complete formula [Don't Know how it got cut ]
=IF(A2<0.25,CHAR(153),IF(A2<=0.5,CHAR(155),IF(A2=0.76,CHAR(152)))))
PS : Use in single line [I have split it to avoid cuts 😉 ]
Hi Chandoo..
why it is not displaying the complete formula..
anyways here is the balance
"=IF(A2<0.25,CHAR(153), IF(A2<=0.5,CHAR(155), IF(A2=0.76,CHAR(152)))))"
@Rohit... your formulas are fine. Just that the width of comment area is fixed and hence my website is cropping it at 640pixels. I just edited your formula and added few white spaces so that it wraps nicely.
Very good idea btw.. kudos!
Hi,
Maybe just go for 'bold' ; 'underline' or 'italic' to draw the users attention? Those methods (if those can be called methods) are used cross media type (books, journals, blogs, billboards, ...) to guide the readers eye to valuable information.
Just a basic thought
@Tom.. good idea..
[...] has a very nice writeup on how to add such alerts to dashboard sheets. Possibly related posts: (automatically generated)Divide your data set into workbooksHow to enforce [...]
Hi Chandoo,
You certainly grabbed my attention! although I wasn't sure what my brother (Suresh) and cousin (Shyam) were doing right, and I was doing wrong? 😉
I love your blog btw - Many thanks for all your hard work in unravelling the secrets and mysteries of Excel!
Best regards
Ramesh
I thought I saw an advertisment for a book about learning excel called excel himalaya or something. It cost about 35.00 us money but seemed to have the things I need to have my admin assistant to start to use. I was hoping to start with this book and then send her to school if she shows some interest and aptitude. Any help on this would be appreciated. Thanks
Great web site and information!!!!
@Jeff... checkout http://chandoo.org/wp/2010/08/25/excel-everest-review/
thanks, your website is awesome!
[...] Alerts to highlight focus areas [...]
[...] There are lots of numbers in this dashboard. I would suggest adding few more visualizations like showing indicators or applying conditional formatting or replacing a table with a chart. This would reduce the [...]
[...] is the same technique as alert icons in dashboard. Just that I also showed green [...]
[...] is the same technique as alert icons in dashboard. Just that I also showed green [...]
Hi Chandoo
Firstly thanks for all the cool tips on how to use Excel better.
I am new to the site and have a question which you may be able to assist with but dont know if these comment boxes are the best way of asking ?
I am looking at assets and trying to calculate the depreciation total by taking a year (say 2010) adding the expected life of the asset (say 10 years) then comparing that to a future date (say 2015) using an IF statement. The calculation in normal is - IF((year in col B (2010) plus 10years)>year 2015, add a years depreciation, otherwise leave blank). The converted date value does not appear able to add 10 years in order to compare it to 2015. Am I missing something ?
I use the “IF” Statement in conjunction with Conditional Formatting in MS Excel to give verbiage to alert one of a required action, dependant on a review date. This makes a visual stimulus, plus it clues one as to what the conditional format is trying to warn you about and what follow-up actions are required.
Wow, I'm really impressed with dashboards. I had no idea this stuff was even possible with excel. I'd like to offer an interactive dashboard to my customers, showing analytics of their data. I have a .pdf file with the datapoints. I'd like them to enter the data on my website, and be able to see their data. Is something like that possible.
Hi Chandoo,
I've recently purchased the package for both templates.
In the portfolio dashboard,under the calculations worksheet, I'm attempting to change the date range in the gantt chart to show only the range of the project that starts in late 2013. How do I do this?
Thanks
Adam
[...] is the same technique as alert icons in dashboard. Just that I also showed green [...]
Hi Chandoo,
I'm new at Excel Dashboard and found your blog really useful and helpful! It's very nice of you that you dedicate your time to do this.
Could you please explain how can I use Alerts based on dates on a Dashboar?
For example, if a target date is coming closer to the actual date, the alert is yellow or red.
I'd really appreciate some help!
Thank you
Where can I download the file Excel of Averall Statistics ???
Thanks a lot.