[datatable-help] A[B]?

[Michael Smith]

See FAQ 2.14
http://datatable.r-forge.r-project.org/datatable-faq.pdf


On 05/04/2014 02:00 PM, Rguy wrote:
> I am beginning to learn the data.table package. At the outset,
> 'data.table.pdf' states:
> 
> It is inspired by A[B] syntax in R where A is a matrix and B is a 2-column
> matrix.
> 
> I have used matrices in R but am unfamiliar with the A[B] syntax. When I
> check the documentation for 'matrix' I find no discussion of such syntax. So
> this "explanation" is in fact a black hole. Please tell your readers what
> the package does in such a way that they are not sent on a wild goose chase.
> For example:
> 
> The data.table package supports an A[B] syntax where A is a data table, B is
> a 2 column data table, and the effect of the expression A[B] is...
> 
> What does A[B] accomplish?
> 
> Thanks.
> 
> 
> 
> 
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