columns selection error
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Assessment
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Newbie friendliness
- 35/100
Research direction
Reproduce the reported data.table examples using dynamic column selection with paste(...), .SDcols, with=F, and conditional assignment. Compare the successful and failing forms, then define the expected behavior and add regression coverage for the incorrect-subscript or unused-argument error.
Written by the indexing model from the issue text.
Description
hi all,
There is a problem to select columns. Suppose we have a data.table t <- data.table(a1 = c(1, 2), a2 = c(3, 4), a3= c(5, 6)). I can get same result by using t[,c("a1","a2","a3")] or t[,paste("a",1:3,sep = "")]. When doing dynamic selection, the thing is different. By using t[,paste("a",1:l,sep = "")] where l=3, only result can be got is "a1" "a2" "a3". To solve this, t[,paste("a",1:l,sep = ""),with=F] works fine. But it cause error when using t[, paste("a", 1:3, sep = "")][t[, .SD > 3, .SDcols = paste("a", 1:3, sep = "")]]<-1 which assigns 1 to irregular position with condition that element is larger than 3. The error is "incorrect number of subscripts on matrix" or "unused argument (with = F)" depends on where with=F is used.The version of data.table is 1.10.0.
Any suggestions?
Best
Xiaotong
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