CODEWITHSUNDEEP
rdata.table
Grec001
Grec001

Reputation: 1121

data.table gives the error: "logical error. i is not a data.table, but 'on' argument is provided"

Given the code as following.

library(data.table)

dt <- data.table(V1=round(runif(9,100,999),2), V2=rep(1:3,3),
                 V3=round(runif(9,10,99),2), V4=rep(letters[1:3],3))
setindex(dt,V4)

F1 <- dt[V2==2 & V3>=3, max(V1)]            
F2 <- dt[V2==2 & V3>=3, max(V1), on = "V4"]

I am 100% sure that class(dt) is "data.table, data.frame" and it runs well with F1, but comes the error of

logical error. i is not a data.table, but 'on' argument is provided.

when F2?

Why? How to solve it?

What I am trying to do is not subsetting(or grouping), but to improve the calculation efficiency with the "on" command which I was told is the keyword for secondary indexing. Many thanks.

I know where I made a mistake. Simply bcs I am using it in the wrong way. i is always a data.table when "on" command is given.

My original purpose is to search for the target efficiently.

condition: V3>=3, and V2==2 target: max(V1)

I can't pass i a condition, but I can make i a data.table as following.

F2 <- dt[V3>=3][V2==2,max(V1), on = "V4"]

it runs perfectly! Thanks guys.

Upvotes: 1

Views: 1339

Answers (1)

AdamO
AdamO

Reputation: 4910

You're not using the right subset syntax. You must have some objects in the workspace named V2 or V3. data.table thinks you're merging them. The i argument is the first argument to [.data.table. Replace V2==2 & V3>=3 with (V2==2 & V3>=3) to refer to the column variables. See here about the subtleties of scoping with i= as a subset in [.data.table. The last on should probably be by (although you would still have had an error because of the subset syntax).

Upvotes: 2

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