I recently came across The R Inferno written by Patrick Burns. In a satirical style following Dante's Inferno, he discusses pretty much every stack exchange question I've ever looked up. Among the many new things I learned and immediately implemented: - the amazing "drop = FALSE" argument that prevents subscripted matrices from dropping a dimension and becoming vectors
"NOTE: Failing to use drop=FALSE inside functions is a major source of bugs. " Suppose you have a matrix my.Matrix and you want to take some subset my.subset of the rows in M.
> M[ my.subset, ] If my.subset has length 1, then the above code will return a single vector. > M[ my.subset, , drop = FALSE] Even if my.subset has length 1, the above will return a matrix with a single row. |
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