[R] Calculating the total change in shareprice over a time periond

[e-mail ma015k3113]

Dear All, I have a data frame which is structured as follows:


COMPANY_NUMBER 	COMPANY_NAME 	CITY 	YEAR_END_DATE 	CLOSE_SHARE_PRICE
22705 	CARDIFF PROPERTY PUBLIC LIMITED COMPANY 	(THE)Egham 	30/09/2005 	NA
22705 	CARDIFF PROPERTY PUBLIC LIMITED COMPANY 	(THE)Egham 	30/09/2006 	NA
22705 	CARDIFF PROPERTY PUBLIC LIMITED COMPANY 	(THE)Egham 	30/09/2007 	9.65
22705 	CARDIFF PROPERTY PUBLIC LIMITED COMPANY 	(THE)Egham 	30/09/2008 	6.55
22705 	CARDIFF PROPERTY PUBLIC LIMITED COMPANY 	(THE)Egham 	30/09/2009 	6.55
22705 	CARDIFF PROPERTY PUBLIC LIMITED COMPANY 	(THE)Egham 	30/09/2010 	7.5
10395804 	TOC PROPERTY BACKED LENDING TRUST PLC 	Newcastle Upon Tyne 	30/11/2016 	NA
10395804 	TOC PROPERTY BACKED LENDING TRUST PLC 	Newcastle Upon Tyne 	30/11/2017 	1.04
10395804 	TOC PROPERTY BACKED LENDING TRUST PLC 	Newcastle Upon Tyne 	30/11/2018 	1.04
SC192761 	MARTIN CURRIE GLOBAL PORTFOLIO TRUST PLC 	Edinburgh 	31/01/2000 	NA
SC192761 	MARTIN CURRIE GLOBAL PORTFOLIO TRUST PLC 	Edinburgh 	31/01/2001 	NA
SC192761 	MARTIN CURRIE GLOBAL PORTFOLIO TRUST PLC 	Edinburgh 	31/01/2003 	NA
SC192761 	MARTIN CURRIE GLOBAL PORTFOLIO TRUST PLC 	Edinburgh 	31/01/2004 	NA
SC192761 	MARTIN CURRIE GLOBAL PORTFOLIO TRUST PLC 	Edinburgh 	31/01/2005 	NA
SC192761 	MARTIN CURRIE GLOBAL PORTFOLIO TRUST PLC 	Edinburgh 	31/01/2006 	1.09
SC192761 	MARTIN CURRIE GLOBAL PORTFOLIO TRUST PLC 	Edinburgh 	31/01/2007 	1.17
SC192761 	MARTIN CURRIE GLOBAL PORTFOLIO TRUST PLC 	Edinburgh 	31/01/2008 	1.24
SC192761 	MARTIN CURRIE GLOBAL PORTFOLIO TRUST PLC 	Edinburgh 	31/01/2009 	0.9
SC192761 	MARTIN CURRIE GLOBAL PORTFOLIO TRUST PLC 	Edinburgh 	31/01/2010 	1.14



I am trying to calculate the total change in share price like for CARDIFF PROPERTY PUBLIC LIMITED COMPANY the total change

between 2005 and 2006 is NA and for 2006 and 2007 it is NA for 2007 and 2008 it is -3.1 and 2008 and 2009 it is 0 and 2009 and 2010 it is +.95. 


I am trying to achieve this via he following code:

for (i in 1:(nrow(PLC)-1))
if (isTRUE (PLC[i, 1] == PLC[i + 1, 1]))
{
PLC$CH_SH_PRICE(i+1) = (PLC$CLOSE_SHARE_PRICE[i+1] -
PLC$CLOSE_SHARE_PRICE[i])
}


I get the following error


Error in 1:(nrow(PLC) - 1) : argument of length 0


Can you kindly suggest any solution to this issue?


Thanks in advance.
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