Hi Maybe you does not need if or ifelse but just divide by years difference.
d2<-ddply(df1,"co_code1",transform, growth=c(NA,exp(diff(log(sales1))/diff(fyear1))- 1)*100) Cheers Petr > -----Original Message----- > From: R-help [mailto:r-help-boun...@r-project.org] On Behalf Of Berend > Hasselman > Sent: Thursday, December 15, 2016 1:18 PM > To: Brijesh Mishra <brijeshkmis...@gmail.com> > Cc: r-help mailing list <r-help@r-project.org> > Subject: Re: [R] Computing growth rate > > > > On 15 Dec 2016, at 04:40, Brijesh Mishra <brijeshkmis...@gmail.com> > wrote: > > > > Hi, > > > > I am trying to calculate growth rate (say, sales, though it is to be > > computed for many variables) in a panel data set. Problem is that I > > have missing data for many firms for many years. To put it simply, I > > have created this short dataframe (original df id much bigger) > > > > df1<-data.frame(co_code1=rep(c(1100, 1200, 1300), each=7), > > fyear1=rep(1990:1996, 3), sales1=rep(seq(1000,1600, by=100),3)) > > > > # this gives me > > co_code1 fyear1 sales1 > > 1 1100 1990 1000 > > 2 1100 1991 1100 > > 3 1100 1992 1200 > > 4 1100 1993 1300 > > 5 1100 1994 1400 > > 6 1100 1995 1500 > > 7 1100 1996 1600 > > 8 1200 1990 1000 > > 9 1200 1991 1100 > > 10 1200 1992 1200 > > 11 1200 1993 1300 > > 12 1200 1994 1400 > > 13 1200 1995 1500 > > 14 1200 1996 1600 > > 15 1300 1990 1000 > > 16 1300 1991 1100 > > 17 1300 1992 1200 > > 18 1300 1993 1300 > > 19 1300 1994 1400 > > 20 1300 1995 1500 > > 21 1300 1996 1600 > > > > # I am now removing a couple of rows > > df1<-df1[-c(5, 8), ] > > # the result is > > co_code1 fyear1 sales1 > > 1 1100 1990 1000 > > 2 1100 1991 1100 > > 3 1100 1992 1200 > > 4 1100 1993 1300 > > 6 1100 1995 1500 > > 7 1100 1996 1600 > > 9 1200 1991 1100 > > 10 1200 1992 1200 > > 11 1200 1993 1300 > > 12 1200 1994 1400 > > 13 1200 1995 1500 > > 14 1200 1996 1600 > > 15 1300 1990 1000 > > 16 1300 1991 1100 > > 17 1300 1992 1200 > > 18 1300 1993 1300 > > 19 1300 1994 1400 > > 20 1300 1995 1500 > > 21 1300 1996 1600 > > # so 1994 for co_code1 1100 and 1990 for co_code1 1200 have been > > removed. If I try, > > d<-ddply(df1,"co_code1",transform, growth=c(NA,exp(diff(log(sales1)))- > 1)*100) > > > > # this apparently gives wrong results for the year 1995 (as shown > > below) as growth rates are computed considering yearly increment. > > > > co_code1 fyear1 sales1 growth > > 1 1100 1990 1000 NA > > 2 1100 1991 1100 10.000000 > > 3 1100 1992 1200 9.090909 > > 4 1100 1993 1300 8.333333 > > 5 1100 1995 1500 15.384615 > > 6 1100 1996 1600 6.666667 > > 7 1200 1991 1100 NA > > 8 1200 1992 1200 9.090909 > > 9 1200 1993 1300 8.333333 > > 10 1200 1994 1400 7.692308 > > 11 1200 1995 1500 7.142857 > > 12 1200 1996 1600 6.666667 > > 13 1300 1990 1000 NA > > 14 1300 1991 1100 10.000000 > > 15 1300 1992 1200 9.090909 > > 16 1300 1993 1300 8.333333 > > 17 1300 1994 1400 7.692308 > > 18 1300 1995 1500 7.142857 > > 19 1300 1996 1600 6.666667 > > # I thought of using the formula only when the increment of fyear1 is > > only 1 while in a co_code1, by using this formula > > > > d<-ddply(df1, > > "co_code1", > > transform, > > if(diff(fyear1)==1){ > > growth=(exp(diff(log(df1$sales1)))-1)*100 > > } else{ > > growth=NA > > }) > > > > But, this doesn't work. I am getting the following error. > > > > In if (diff(fyear1) == 1) { : > > the condition has length > 1 and only the first element will be used > > (repeated a few times). > > > > # I have searched for a solution, but somehow couldn't get one. Hope > > that some kind soul will guide me here. > > > > In your case use ifelse() as explained by Rui. > But it can be done more easily since the fyear1 and co_code1 are > synchronized. > Add a new column to df1 like this > > df1$growth <- c(NA, > ifelse(diff(df1$fyear1)==1, > (exp(diff(log(df1$sales1)))-1)*100, > NA > ) > ) > > and display df1. From your request I cannot determine if this is what you > want. > > regards, > > Berend Hasselman > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting- > guide.html > and provide commented, minimal, self-contained, reproducible code. ________________________________ Tento e-mail a jakékoliv k němu připojené dokumenty jsou důvěrné a jsou určeny pouze jeho adresátům. Jestliže jste obdržel(a) tento e-mail omylem, informujte laskavě neprodleně jeho odesílatele. Obsah tohoto emailu i s přílohami a jeho kopie vymažte ze svého systému. Nejste-li zamýšleným adresátem tohoto emailu, nejste oprávněni tento email jakkoliv užívat, rozšiřovat, kopírovat či zveřejňovat. Odesílatel e-mailu neodpovídá za eventuální škodu způsobenou modifikacemi či zpožděním přenosu e-mailu. 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