j not evaluated in data.table environment

[ChHaeni]

Ehm, possibly it is just me (and I'd be really embarrassed and sorry if so!).
As the title says, I have the problem, that j is not evaluated in the data.table environment any longer. Small example:

x <- data.table(1:3)
x[,3]
x[,"test"]

gives the following errors:

Error in [.data.table(x, , 3) : Item 1 of j is 3 which is outside the column number range [1,ncol=1]

and

Error in [.data.table(x, , "test") : column(s) not found: test

Sorry, if I'm missing something...
My sessionInfo:

R version 3.3.2 (2016-10-31)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

locale:
[1] LC_COLLATE=German_Switzerland.1252  LC_CTYPE=German_Switzerland.1252   
[3] LC_MONETARY=German_Switzerland.1252 LC_NUMERIC=C                       
[5] LC_TIME=German_Switzerland.1252    

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] data.table_1.9.8

loaded via a namespace (and not attached):
[1] tools_3.3.2

[shrektan]

Check the NEWS.md

When j contains no unquoted variable names (whether column names or not), with= is now automatically set to FALSE. Thus, DT[,1], DT[,"someCol"], DT[,c("colA","colB")] and DT[,100:109] now work as we all expect them to; i.e., returning columns, #1188, #1149. Since there are no variable names there is no ambiguity as to what was intended. DT[,colName1:colName2] no longer needs with=FALSE either since that is also unambiguous. That is a single call to the : function so with=TRUE could make no sense, despite the presence of unquoted variable names. These changes can be made since nobody can be using the existing behaviour of returning back the literal j value since that can never be useful. This provides a new ability and should not break any existing code. Selecting a single column still returns a 1-column data.table (not a vector, unlike data.frame by default) for type consistency for code (e.g. within DT[...][...] chains) that can sometimes select several columns and sometime one, as has always been the case in data.table. In future, DT[,myCols] (i.e. a single variable name) will look for myCols in calling scope without needing to set with=FALSE too, just as a single symbol appearing in i does already. The new behaviour can be turned on now by setting the tersely named option: options(datatable.WhenJisSymbolThenCallingScope=TRUE). The default is currently FALSE to give you time to change your code. In this future state, one way (i.e. DT[,theColName]) to select the column as a vector rather than a 1-column data.table will no longer work leaving the two other ways that have always worked remaining (since data.table is still just a list after all): DT[["someCol"]] and DT$someCol. Those base R methods are faster too (when iterated many times) by avoiding the small argument checking overhead inside the more flexible DT[...] syntax as has been highlighted in example(data.table) for many years. In the next release, DT[,someCol] will continue with old current behaviour but start to warn if the new option is not set. Then the default will change to TRUE to nudge you to move forward whilst still retaining a way for you to restore old behaviour for this feature only, whilst still allowing you to benefit from other new features of the latest release without changing your code. Then finally after an estimated 2 years from now, the option will be removed.

[ChHaeni]

Thank you! Next time I'll check the NEWS.md before posting...