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For a vector of logical values, why does R allocate 4 bytes, when a bit vector would consume 1 bit per entry? (See this question for examples.) Now, I realize that R also facilitates storage of NA values, but couldn't that be done with an additional bit vector? In other words, why isn't it enough to just use a cheap two bit data structure? For what it's worth, Matlab uses 1 byte for logicals, though it doesn't facilitate NA values. I'm not sure why MathWorks isn't satisfied with one bit functionality, much less a two bit data structure, but they have fancy pants marketers... [I'm gonna milk "two bit" for all it's worth in this question. ;-)] Update 1. I think that the architecture reasons offered make some sense, but that feels a little ex post facto. I haven't checked 32 bit or 16 bit R to see how large their logicals are - that could lend some support to the idea. It seems, from the R Internals manual that logical vectors (LGLSXP) and integers (INTSXP) are 32 bits on every platform. I can understand a universal size for integers, independent of word size. Similarly, storage of logicals also seems to be independent of word size. But it's so BIG. :) In addition, if the word size argument is so powerful, it seems strange to me to see Matlab (I think it's a 32 bit Matlab) consume only 1 byte - I wonder if MathWorks chose to be more memory efficient with a tradeoff for programming complexity and some other overhead for finding sub-word objects. Also, there are certainly other options in are: as Brian Diggs notes, the bit package facilitates bit vectors, which was very useful for the problem in the question above (an 8X-10X speedup for the task was obtained by converting f

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