R help - Jul 1999 - eval(), expression()

"Wolfgang Koller" <koller2 at fgr.wu-wien.ac.at> writes:
> Dear R-Users!
> 
> My aim is to produce boxplots without the outliers included in the 
> plot. I started to write a function that looks something like:
> 
> myboxplot <-function(x,fa) {
>   bpdata <- boxplot(x~fa,plot=FALSE)
>   bpnames <- names(bpdata)
>   for (JJ in bpnames) { 
>     command <- paste("bpdata$",JJ,"$out <-
numeric(0)",sep="");
>     eval(command)
>   }
>   bxp(bpdata)
> }
> 
> Obviously this does not work as I intended since the argument 
> of eval() should be of type expression. However, with 
> expression() there is no way to have variable JJ evaluated first.
> 
> Does anybody see a way to solve this problem?
bp <- boxplot(..etc..)
for (n in names(bp)) bp[[n]]$out<-numeric(0)

-- 
   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
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Dear R-Users!

My aim is to produce boxplots without the outliers included in the 
plot. I started to write a function that looks something like:

myboxplot <-function(x,fa) {
  bpdata <- boxplot(x~fa,plot=FALSE)
  bpnames <- names(bpdata)
  for (JJ in bpnames) { 
    command <- paste("bpdata$",JJ,"$out <-
numeric(0)",sep="");
    eval(command)
  }
  bxp(bpdata)
}

Obviously this does not work as I intended since the argument 
of eval() should be of type expression. However, with 
expression() there is no way to have variable JJ evaluated first.

Does anybody see a way to solve this problem?

Thanks for any suggestions!

Wolfgang Koller

P.S.: Similar problems with expression() can arise with producing 
annotations in plots.




----------------------------------------------------------
Wolfgang Koller,  koller2 at fgr.wu-wien.ac.at
Research Institute for European Affairs
Vienna University of Economics and Business Administration
Althanstrasse 39-45, 1090 Vienna, Austria
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On Tue, 6 Jul 1999, Wolfgang Koller wrote:
> Dear R-Users!
> 
> My aim is to produce boxplots without the outliers included in the 
> plot. I started to write a function that looks something like:
> 
> myboxplot <-function(x,fa) {
>   bpdata <- boxplot(x~fa,plot=FALSE)
>   bpnames <- names(bpdata)
>   for (JJ in bpnames) { 
>     command <- paste("bpdata$",JJ,"$out <-
numeric(0)",sep="");
>     eval(command)
>   }
>   bxp(bpdata)
> }
> 
> Obviously this does not work as I intended since the argument 
> of eval() should be of type expression. However, with 
> expression() there is no way to have variable JJ evaluated first.

There are various possibilities. One is just to 
write
   for(JJ in names(bpdata))
	bpdata[[JJ]]$out<-numeric(0)

without all that parsing and deparsing.

In a situation where this doesn't work you can use substitute()

for(nn in names(bpdata){
command<-substitute(expression(bpdata$JJ$out<-numeric(0)),list(JJ="1"))
eval(eval(command))
}

This sort of thing is sometimes useful for annotating plots.


Thomas Lumley
Assistant Professor, Biostatistics
University of Washington, Seattle


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