[R] two questions for R beginners

[Karl Ove Hufthammer]

On Thu, 25 Feb 2010 17:31:19 +0000 Patrick Burns 
<pburns at pburns.seanet.com> wrote:
> * What were your biggest misconceptions or
> stumbling blocks to getting up and running
> with R?

I didn't have any major stumbling blocks, but even after years of using 
R I didn't have a clear concept of what exactly a vector, a list and a 
data frame was, and what was the difference and similarities between 
them (and stuff like why does x[i] return a different result than 
x[[i]]).

Some things that have tripped my up is reassigning the value of T or F 
and getting very strange results afterwards (I now use only TRUE and 
FALSE). FAQ 7.31 and 7.22 have also been troublesome at times, 
especially 7.31 when used in 'for' loops.

Also I found it quite confusing that

?ifelse

works, but not

?if

(you have to type ?"if")

Also, why ?plot didn't give me the information I was looking for but
?plot.default did was rather confusing. I still experience similar 
problems with other functions. Usually 'methods' help, but some packages 
use S4 methods, which makes finding the correct help package quite 
challenging at times.

> * What documents helped you the most in this
> initial phase?

In the initial phase I found the Rtips 
"http://pj.freefaculty.org/R/Rtips.html"
extremely useful.

For understanding the difference between the various data types in R, 
Phil Spector's wonderful book 'Data Manipulation with R' was a great 
help. When reading it I finally understood things I have been wondering 
about for years. It really like the book. It's short, crystal clear and 
immensely useful.

Another very useful document of a more advanced nature is the R Inferno. 
Best read after you've been using R for some time, though.

I'm over the initial phase now, but two resources which continue to be 
of great help is http://www.rseek.org/ (mainly for searching the mailing 
list) and the 'sos' package (for finding the functions and packages I 
need). 'sos' really is great. There have been other packages/functions 
trying to do the same thing, but they have been to time-consuming and 
difficult to use (and learn), typically requiring you to first do a 
search, and then do some advanced subsetting to get useful results. This 
is similar to older search engines requiring many boolean terms to give 
the needed search results. With 'sos' I just choose some simple search 
terms describing what I'm looking for, and immediately get relevant 
results. 'sos' really is the Google of the R world. It has made a great 
impact on the discoverability of the various R functions and packages.

Lastly, the 'demo' function is seldom mentioned, and easy to overlook, 
but gives a nice (and sometimes impressive) overview of what type of 
graphics is possible to create with a given packages. I wish more 
packages would have well-written demos. Also, I think some of the 
examples from the 'example' sections of help pages for functions could 
very well be copied to the demo of the corresponding package, e.g. a few 
of the examples of the 'xyplot' function in 'lattice'.

-- 
Karl Ove Hufthammer