[R] general help on R and factor in R and a few simple comment from a newbie
Gabor Grothendieck
ggrothendieck at gmail.com
Mon May 1 00:27:46 CEST 2006
On 4/30/06, Guojun Zhu <shmilylemon at yahoo.com> wrote:
> Hi. I am starting to learn R for a course project. I
> am relative OK c++ programer. I found the R is very
> different. I have read the "an introduction to R". I
> have to say it is not very newbie friendly. It does
> not explain many things clearly. And unfortunately,
> there is not too much introductory materials available
> on-line. I do not want to buy a book.
Enter
R
into google and you get the R home page. On the left pane of that
under Documentation click on Other and from there click on
Contributed Documentation and there is a list of literally dozens
of different introductions.
Also google for
zoonekynd R
for another online intro to R.
>
> For example, I found factor is a quite different
> concept.I cannot use it as a vector which I can
> somehow think as a 1-dimension array. help(factor)
> does not help much to clear about the concept either.
> Also there are quite few basic concepts like the data
> structure of model, etc is far from clear for me. Yet
> there is no general place I can look for there more
> general idea.
>
> help is a very interesting and useful function.
> However, I would say the content lacks some general
> idea. I used to learn Mathematica, which is also a
> high-level tool by their help. It is very
> comprehensive, yet well-organized with some general
> idea, some specific fundtion explanation and some
> functions about one topic. For R's help, you get only
> the specific explanation for the perticular function,
> and no more related things. I feel it is more like a
> reference for experienced user instead of some newbie.
>
>
>
> I know there should be some trick by R with some dense
> code for big work. But unfortunately, I could not
> find many place to learn it.
>
>
> Now for a specific question,
>
> I use read.csv to read some data from an excel data
> file (about 30,000 line data). Some columns has empty
> data, so NA was read. But they were read in as a
> factor instead of vector. I need to manipulate them
> later as a vector (for example standardizing by
> dividing with standard deviation, or derive a new
> column from other two or more columns). How to
> convert it into vector? Or maybe some functions
> already exists for factor already?
>
Check out the na.strings= and possibly the as.is = TRUE
arguments on read.table. Also the read.xls command
from the gdata package may be helpful.
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