R help - Oct 2001 - Fw: eval and as.symbol question

----- Original Message -----
From: "Kaspar Pflugshaupt" <pflugshaupt at geobot.umnw.ethz.ch>
To: "Gary Collins" <gco at eortc.be>
Cc: "r-help" <r-help at stat.math.ethz.ch>
Sent: Thursday, October 18, 2001 2:19 PM
Subject: Re: [R] eval and as.symbol question

> On 18.10.2001 13:46 Uhr, Gary Collins wrote:
>
> > But when I merge these into a dataframe with colnames(df)<-
> >
c("c1","c2","c3","c4","c5"),
so that
> >> df
> > c1 c2 c3 c4 c5
> > 1  1  1 NA NA NA
> > 2  2  2 NA NA NA
> > 3  3  3 NA NA NA
> > 4 NA NA NA  1  1
> > 5  2  2  2  2  2
> > 6  2  2  2  2  2
> > 7 NA  3  3 NA  2
> >
> > and try the next "logical" step from above....
> >
>
> You might try something like this instead:
>
> apply(df, 2, function(x) sum(is.na(x)))
>
>
>
> Hope this helps
>
> Kaspar
I want to avoid this. I know how the apply function works. The counting
missing items was merely an example, there are a number of ways to solve
that particular problem. My question is how to use as.symbol, eval and paste
to get the required result as I will use very similar steps.

Thanks
Gary
__________________________________________________
Dr. Gary S. Collins,
Statistics Research Fellow,
Quality of Life Unit,
European Organisation for Research and Treatment of Cancer,
EORTC Data Center,
Avenue E. Mounier 83, bte. 11,
B-1200 Brussels, Belgium.

Tel: +32 2 774 1 606
Fax: +32 2 779 4 568
http://www.eortc.be/home/qol/
__________________________________________________


-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at
stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._

"Gary Collins" <gco at eortc.be> writes:

> >
> > You might try something like this instead:
> >
> > apply(df, 2, function(x) sum(is.na(x)))
> >
> >
> >
> > Hope this helps
> >
> > Kaspar
> 
> I want to avoid this. I know how the apply function works. The counting
> missing items was merely an example, there are a number of ways to solve
> that particular problem. My question is how to use as.symbol, eval and
paste
> to get the required result as I will use very similar steps.
You should probably reconsider the hint from Kaspar that you might
want a more structured solution. Manipulation of code via text strings
is usually not The Right Way of doing things. 

However, if you must, you need to notice that as.symbol creates a
symbol from *any* textstring
> "]{" <- 5
> eval(as.symbol( "]{"))
[1] 5

However a$b is usually not a single symbol but three, an indexing
expression consisting of a, $, and b. If you want to get that from a
text string you need parse("a$b").

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at
stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._