I have a datatable with 3 categorical variables: primarydx, NumDx, and ContractType.
primarydx <- rep(c("AB","MT"),10)
NumDx <- rep(c(1,2,3), length.out=20 )
ContractType <- rep( c("W","L","W","W","W") , length.out=20)
SecDx3 <- data.table(primarydx, NumDx, ContractType)
I want to calculate the percentage of records of each ContractType within primarydx and NumDx. The following code works:
Num <-SecDx3[ , .(n=.N), by=.(primarydx, NumDx, ContractType)]
denom <- SecDx3[ , .(d=.N), by=.(primarydx, NumDx)]
pct <- merge(Num,denom)
pct[,pct:=n/d][]
Is there a better way?
I did find something like:
SecDx3[,{
d =.N
.SD[, .(pct = .N/d), by=.(primarydx, NumDx, ContractType)]
}, by=.(primarydx, NumDx)]
but this returns an error "The items in the 'by' or 'keyby' list are length (1,1,20). Each must be same length as rows in x or number of rows returned by i (20)." which I don't understand.
Thanks for your help,
David
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