[R] confusion with R syntax
Leeds, Mark (IED)
Mark.Leeds at morganstanley.com
Thu Oct 11 21:34:22 CEST 2007
I just noticed something by accident with R syntax that I'm sure is
correct but I don't understand it. If I have
a simple numeric vector x and I subscript it, it seems that I can then
subscript a second time with TRUE
or FALSE, sort of like a 2 dimensional array in C. Does someone know if
this is documented somewhere
Because it's neat but I never knew it existed. To me it seems like a 1
dimensional vector should
have only one dimensional indexing ?
x <- seq(1,10)
> x
[1] 1 2 3 4 5 6 7 8 9 10
> x[2:4][c(TRUE,FALSE,TRUE)]
[1] 2 4
But, it only works for TRUE or FALSE and not numbers so I think it's not
really 2 dimensional indexing.
x[1][2]
[1] NA
If someone could explain this mechanism or tell me what I should look
for in the archives, it would
be appreciated. Thanks.
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