R help - Apr 2006 - general help on R and factor in R and a few simple comment from a newbie

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.  

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?

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.