R help - Feb 2010 - "get" problem

Dear R communtiy,
   I do not understand why this does not work...:
> betaS$SBP
[1]  0.03274 -0.04216 -0.08986 -0.45980  0.60320 -0.63070 -0.05682 
0.20130
> t<-c("betaS$SBP")
> t
[1] "betaS$SBP"
> get(t)
Error in get(t) : object 'betaS$SBP' not found


[I am trying to use the variable "t" in a loop to call many different
objects, but the pasting together did not work and this simple example does
not neither...]

Thank you and best regards, Georg.
*******************
Georg Ehret
JHU
Baltimore

	[[alternative HTML version deleted]]

On 2/24/10, Georg Ehret <georgehret at gmail.com>
wrote:
>    I do not understand why this does not work...:
>
Previously I ran into this and I am also curious why it doesn't work,
but you can work around so:
> x <- NULL
> x$a <- 1:10
> x$b <- 11:20
> x
$a
 [1]  1  2  3  4  5  6  7  8  9 10

$b
 [1] 11 12 13 14 15 16 17 18 19 20
> get("x")[ "a"]
$a
 [1]  1  2  3  4  5  6  7  8  9 10
> get("x")[ "b"]
$b
 [1] 11 12 13 14 15 16 17 18 19 20
> t <- "a"
> get("x")[ t]
$a
 [1]  1  2  3  4  5  6  7  8  9 10


Liviu

On Feb 24, 2010, at 4:31 PM, Georg Ehret wrote:
> Dear R communtiy,
>   I do not understand why this does not work...:
>
>> betaS$SBP
> [1]  0.03274 -0.04216 -0.08986 -0.45980  0.60320 -0.63070 -0.05682   
> 0.20130
>> t<-c("betaS$SBP")
>> t
> [1] "betaS$SBP"
>> get(t)
> Error in get(t) : object 'betaS$SBP' not found
A couple of different ways of passing multi-element objects to loops:

 > tt <- scan()
1:  0.03274 -0.04216 -0.08986 -0.45980  0.60320 -0.63070 -0.05682   
0.20130
9:
Read 8 items
 > tt
[1]  0.03274 -0.04216 -0.08986 -0.45980  0.60320 -0.63070 -0.05682   
0.20130
 > for (xi in seq(tt)) print(xi)
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 6
[1] 7
[1] 8
 > for (xi in seq(tt)) print(tt[xi])
[1] 0.03274
[1] -0.04216
[1] -0.08986
[1] -0.4598
[1] 0.6032
[1] -0.6307
[1] -0.05682
[1] 0.2013

 > beta <-list()
 > beta$SBP <- tt
 > beta["SBP"]
$SBP
[1]  0.03274 -0.04216 -0.08986 -0.45980  0.60320 -0.63070 -0.05682   
0.20130

 > for (xi in seq_along(beta$SBP) ) print(xi)
[1] 1
[1] 2
[1] 3
[1] 4
[1] 5
[1] 6
[1] 7
[1] 8

 > for (xi in beta$SBP)  print(xi)
[1] 0.03274
[1] -0.04216
[1] -0.08986
[1] -0.4598
[1] 0.6032
[1] -0.6307
[1] -0.05682
[1] 0.2013

-- 
David.
>
>
> [I am trying to use the variable "t" in a loop to call many
different
> objects, but the pasting together did not work and this simple  
> example does
> not neither...]
>
> Thank you and best regards, Georg.
> *******************
> Georg Ehret
> JHU
> Baltimore
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius, MD
Heritage Laboratories
West Hartford, CT

On 24/02/2010 4:31 PM, Georg Ehret wrote:
> Dear R communtiy,
>    I do not understand why this does not work...:
>
> > betaS$SBP
> [1]  0.03274 -0.04216 -0.08986 -0.45980  0.60320 -0.63070 -0.05682  0.20130
> > t<-c("betaS$SBP")
> > t
> [1] "betaS$SBP"
> > get(t)
> Error in get(t) : object 'betaS$SBP' not found
>   
The problem is that betaS$SBP is an expression that extracts a component 
of the betaS object, it's not the name of an object.  get() only gets 
single objects, it doesn't evaluate expressions.  You need something like

eval(parse(text=t))

to get what you want.

Duncan Murdoch
>
> [I am trying to use the variable "t" in a loop to call many
different
> objects, but the pasting together did not work and this simple example does
> not neither...]
>
> Thank you and best regards, Georg.
> *******************
> Georg Ehret
> JHU
> Baltimore
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>