Thank very much ! Indexing is exactly the problem. I think it´s not
because somebody wrote a bad doc, it´s rather because being an amateur
PHP etc scripter i did not realize the power of this indexing yet.
Sometime ago i surely would have used a lot more loops instead of
proper indexing.
Basically i guess this is due to the fact that i was reluctant to
search for ?$. I did simply not consider that this was possible. It´s
always difficult to google respectively search for for operators in
general.
I believe most documentations i read were some minor documentations
made by universities for some basic statistics.
Some popular document i really like is Farnsworth Econometrics in R,
but searching for shortcut it does not offer the result i needed.
Indeed, if i had looked for [[ i would have found something ...
Imho, the indexing is something very special in R, perhaps it would
help newbies if documentations point it out more precisely in its
table of content, using some terminology that might help to find
the part about indexing. e.g. : indexing operators, shortcuts vs.
indexing , or dynamic or computed indexing as you said.
hth
Am 25.11.2008 um 17:13 schrieb Greg Snow:
I think your problem is more with indexing than with function
writing. The main confusion is in how to use '$', this is a
shortcut to make certain things easier, but you are trying to use
the shortcut like going from France to Germany by way of New York
City because you know a great shortcut through NYC.
From the help page for $ (> ?'$'):
"Both '[[' and '$' select a single element of the list. The main
difference is that '$' does not allow computed indices, whereas
'[[' does."
You are trying to use a computed index, look at the line above
(especially the 'not') and see if there is something else there
suggests what you should be using.
This seems to be a common misunderstanding lately, could you tell us
a bit about which documentation and examples you read that lead you
to think about using '$' with computed indices and did not help you
understand the need for '[[' instead so that maybe the documentation
can be improved to help future readers?
--
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
[EMAIL PROTECTED]
801.408.8111
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
project.org] On Behalf Of Bunny, lautloscrew.com
Sent: Tuesday, November 25, 2008 3:18 AM
To: r-help@r-project.org
Subject: [R] basic information defining functions
Hi all,
i am looking from some insights to define own R functions. so far i
found most basics in documentations that are around on the web.
except
for one thing:
I´d like to define some function, say:
#assume my data matrix contains vectors like data$myColumn1,data
$myColumn2 etc.
getMyColumn <- function (columnid){
x<-data$MyColumn?columnid?[data$indexone=1 & data$index2=5]
return(x)
}
Do I need to use assign or eval first ? I tried to use paste to
combine something like: paste("data$MyColumn",columnid,sep="") which
did not work.
I am happy to get any help with the problem, but also thankful for
some useful link or guide on how to define own functions properly,
especially the dynamic naming and return part
thx in advance
bunny
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