[datatable-help] create empty data.table

[statquant3]

My convoluted way

#@usage: create empty vector
newVec <- function(char){
	if(char=='D') return(as.Date(integer(0)))
	if(char=='N') return(numeric(0))
	if(char=='C') return(character(0))
	if(char=='I') return(integer(0))
	return(numeric(0))
}

#@usage: create empty data.table with given types
#@example: 
#	colNames <- c('col1','col2','col3'); colTypes <- 'DNC'; DT <-
emptyDT(colNames,colTypes)
emptyDT <- function(colNames,colTypes){
	DT <- data.table(X=newVec(substr(colTypes,1L,1L)))
	setnames(DT,'X',colNames[1L])
	N <- length(colNames)
	if(N>1){
		for(i in 2:N){
			DT[,X:=newVec(substr(colTypes,i,i))]
			setnames(DT,'X',colNames[i])
		}
	}
	return(DT)
}

R) colNames <- c('col1','col2','col3'); colTypes <- 'DNC'; DT <-
emptyDT(colNames,colTypes)
R) str(DT)
Classes 'data.table' and 'data.frame':  0 obs. of  3 variables:
 $ col1:Class 'Date'  num(0) 
 $ col2: num 
 $ col3: chr 
 - attr(*, ".internal.selfref")=<externalptr> 





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