On Sep 29, 2013, at 5:28 PM, Ista Zahn wrote: > Hi JD, > > On Sun, Sep 29, 2013 at 5:48 PM, john doe <anon.r.u...@gmail.com> wrote: >> I am having trouble understanding how classes in R work. Here is a small >> reproducable example: >> >>> x=1 >>> class(x) >> [1] "numeric" >> >> OK. When a variable is a number, its class is "numeric". Does R have >> multiple types for numbers, like C++ (eg integer, float, double). > > Yes, but the class is not the type: > >> x <- 1:10 >> class(x) > [1] "integer" >> typeof(x) > [1] "integer" >> class(x) <- "foo" >> class(x) > [1] "foo" >> typeof(x) > [1] "integer" > > If so, >> where can I see a list, and how does "numeric" fit into this system? > > A list of what? For a list of storage modes see ?typof. For classes > there cannot be any such list, as you can create a new class as easily > as > > class(x) <- "aNewClassThatNeverExistedBefore" > > >> >>> x=1:100 >>> class(x) >> [1] "integer" >> >> Wait - I thought that I assigned x to be an array/vector of 100 integers >> (numerics). Why is the class not "array" or "vector". How is "integer" >> different than "numeric"? Is there a "vector" or "array" class in R? If >> so, why is this not that? > > See http://cran.r-project.org/doc/manuals/r-release/R-intro.html#Objects > (And while you are there it wouldn't be a bad idea to read the rest of > manual as well). > >> >>> class(x[1]) >> [1] "integer" >> >> This is even more confusing to me. Because x[1] is 1. And the class of >> that was "numeric" in my first example. Why is it integer now? > > Presumably because '[' turned it into one. help("[") says that the > return value is "typically an array-like R object of a similar class > as ‘x’."
If you just type: x <- 1 # the mode is "double" and the class is "numeric" If you type: x <- 1L # mode and class are "integer" x[1] does not coerce an "integer" to "numeric" -- David Winsemius Alameda, CA, USA ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
