st: RE: Change roman to Arabic numerals

[Nick Cox <n.j.cox@durham.ac.uk>]

I think anyone tempted to write this would be best advised to extract the subtraction parts of the syntax first, i.e. CM etc. 

(Also, from what I recall IIII is sometimes allowed as a non-standard variant of IV.) 

Here is one stab. This is a Mata function that works on a string vector of Roman numerals in upper case. 

Example first:

. mata

: stuff = ("IV", "MCMIV")

: roman_to_arabic(stuff)
          1      2
    +---------------+
  1 |     4   1904  |
    +---------------+

: roman_to_arabic(stuff')
          1
    +--------+
  1 |     4  |
  2 |  1904  |
    +--------+

: end

Code second: 

mata : 

real roman_to_arabic(string vector roman) { 
	
	numeric vector ro 
	string vector work 
	ro = J(rows(roman), cols(roman), 0)  
	work = roman 
	
	ro = ro + 900 * (strpos(work, "CM") :> 0) 
	work = subinstr(work, "CM", "", .) 
	ro = ro + 400 * (strpos(work, "CD") :> 0) 
	work = subinstr(work, "CD", "", .) 
	ro = ro + 90 * (strpos(work, "XC") :> 0) 
	work = subinstr(work, "XC", "", .) 
	ro = ro + 40 * (strpos(work, "XL") :> 0) 
	work = subinstr(work, "XL", "", .) 
	ro = ro + 9 * (strpos(work, "IX") :> 0) 
	work = subinstr(work, "IX", "", .) 
	ro = ro + 4 * (strpos(work, "IV") :> 0) 
	work = subinstr(work, "IV", "", .) 
	
	while (sum(strpos(work, "M"))) { 
		ro = ro + 1000 * (strpos(work, "M") :> 0) 
		work = subinstr(work, "M", "", 1) 
	} 
	
	while (sum(strpos(work, "D"))) { 
		ro = ro + 500 * (strpos(work, "D") :> 0) 
		work = subinstr(work, "D", "", 1) 
	} 
	
	while (sum(strpos(work, "C"))) { 
		ro = ro + 100 * (strpos(work, "C") :> 0) 
		work = subinstr(work, "C", "", 1) 
	} 
	
	while (sum(strpos(work, "L"))) { 
		ro = ro + 50 * (strpos(work, "L") :> 0) 
		work = subinstr(work, "L", "", 1) 
	} 
	
	while (sum(strpos(work, "X"))) { 
		ro = ro + 10 * (strpos(work, "X") :> 0) 
		work = subinstr(work, "X", "", 1) 
	} 
	
	while (sum(strpos(work, "V"))) { 
		ro = ro + 5 * (strpos(work, "V") :> 0) 
		work = subinstr(work, "V", "", 1) 
	}
	
	while (sum(strpos(work, "I"))) { 
		ro = ro + (strpos(work, "I") :> 0) 
		work = subinstr(work, "I", "", 1) 
	}
		
	return(ro) 
}	 
	
end 	
	

Nick 
n.j.cox@durham.ac.uk 


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Lachenbruch, Peter
Sent: 17 December 2010 18:50
To: 'statalist@hsphsun2.harvard.edu'
Subject: st: Change roman to Arabic numerals

A colleague wants to generate Arabic numbers from Roman numerals and I was = wondering if anyone has written a routine for this.  She only has I to X so=  I suggested Gen numb=(rom=="I")+2*(rom=="2")+3*(rom=="3")+4*(rom=="4"=
)  etc.
This is OK for this application, but not if we have many numbers.  Of course the ordering  gets messed up - I, II, III, IV, IX, V, VI, VII, VIII, X so=  encode won't work  and gen numb=3Dreal(rom) won't do either.


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