[R] two questions for R beginners
hadley wickham
h.wickham at gmail.com
Mon Mar 1 17:33:14 CET 2010
> Suppose X is a dataframe or a matrix. What would you expect to get from
> X[1]? What about as.vector(X), or as.numeric(X)?
>
> The point is that a dataframe is a list, and a matrix isn't. If users don't
> understand that, then they'll be confused somewhere. Making matrices more
> list-like in one respect will just move the confusion elsewhere. The
> solution is to understand the difference.
What I find more confusing is the behaviour of $ with vectors. In my
mind x$a is a shortcut for writing x[["a"]], but:
> x <- list(a = 1)
> x$a
[1] 1
> x <- c(a = 1)
> x$a
Error in x$a : $ operator is invalid for atomic vectors
> x[["a"]]
[1] 1
Hadley
--
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/
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