Hi all, I'm really new to data.table and something really simple has me stumped.
Lets say I have the following (but much bigger so timing matters) dt = data.table(x=1:100,y=1:2,z=1:4,key="y,z") >From the documentation, I understand that dt[J(1,3)] is significantly faster dt[y==1 & z==3] and I could do dt[J(1)] instead of dt[y==1] but is there any way to do dt[z==3] faster? I want to do something like df[J( ,3)] but I know that doesn't make sense. Is it because z is not the primary key that I can't seem to figure out how to use J to do this? Since it isn't sorted on z anyway I doubt I can get a speed up right?
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