Dear Matthew Thank you for trying to guide me. Unfortunately I was not able to really comprehend what I was reading
I entered the following into google search "site: lists.r-forge.r-project.org/pipermail/datatable-help/ secondary" I got many hits and I could see a discussion but could not fathom how it related to my question. Would love some help from you or someone else. I want to be able to select by a criterion in the second key and accept all possible values in the first key. Farrel Buchinsky Google Voice Tel: (412) 567-7870 On Wed, Jan 18, 2012 at 22:40, Matthew Dowle <[email protected]> wrote: > Hi. Try searching datatable-help for 'secondary'. > > > In setkey it is possible to have multiple columns be a key. There is > > however an order to it. To select all the rows by a particular value in > > the > > first key is easy > > DT[J("a value from the first key")] > > > > It is even quite easy to select by an AND criteria that incorporates the > > second key > > DT[J("a value from the first key","a value from the second key")] > > > > But what happens if one wanted to select by only one criteria being a a > > value that must be present in the second key? I was hoping to get lucky > by > > just leaving it blank. But it did not see to work. > > > > DT[J(,"a value from the second key")] > > > > I would love to know what you do. > > > > > > Farrel > > _______________________________________________ > > datatable-help mailing list > > [email protected] > > > https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help > > > > >
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