[Rd] to overcome error while computing sd for each subset of data (PR#9931)

[anjalishitole at yahoo.co.in]

Full_Name: Anjali Shitole
Version: R 2.5.1
OS: 
Submission from: (NULL) (202.141.157.91)


I want to compute coefficient of variation for each subset of data.
Each subset is heterogeneous means number of rows in each subset are
different.These all subsets are in one dataset situated one by one.
i have used aggregate command to calculate mean for each subset.
But same command for calculating sd gives error 
see the following program,
> a<-read.table("c:/mri/data/ratioinput.txt",header=T, na.strings =
"NA",fill=TRUE)
> dim(a)
[1] 32515    27
> BusinessRisk<-a[,16]/(a[,26]/a[,27]) 
> a1<-a[,1:3]
> a2<-cbind(a1,BusinessRisk)
> c1<-aggregate(BusinessRisk,list(a2[,1]),mean)
> names(a)
 [1] "Co_Code"        "Co_Name"        "Year"           "TotSholderFund"
 [5] "TotLiab"        "NetBlock"       "Investments"    "Inventories"   
 [9] "SundryDebts"    "CashandBank"    "TotCurrAssets"  "CurrLiab"      
[13] "TotCurrLiab"    "TotAssets"      "NetSales"       "OpPft"         
[17] "Interest"       "GrossPft"       "AdjNetPft"      "Dividend"      
[21] "PrefDivi"       "EquityPaidUp"   "CurrentAssets"  "PBIT"          
[25] "TotExpen"       "Equity"         "FaceValue"     
> c2<-aggregate(BusinessRisk,list(a2[,1]),sd(BusinessRisk,na.rm=TRUE))
Error in FUN(X[[1L]], ...) : argument "INDEX" is missing, with no default
> 
Please help me to overcome this error.