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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