Hi,
I'm new to R and looking for a way to use a variable to reference to an
object.
I'm plotting several graphs on top of each other and want to do this by
a for loop. The field I want to graph have names like a1,a2,a3, ...
I can't figure out how to get this working:
It should look like this:
lines(spectral$Wavelength,paste("spectral$a",j,sep=""),col=j)
but the "paste()" does not seem to work in this context.
Any help?
Kind regards,
Kris
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get() is your friend; e.g.
plot(get(paste("x",1, sep="")), get(paste("x", 2,
sep="")))
Andy
-----Original Message-----
From: Kris Nackaerts [mailto:kris.nackaerts at agr.kuleuven.ac.be]
Sent: Friday, November 22, 2002 11:22 AM
To: r-help at stat.math.ethz.ch
Subject: [R] Use of variables to reference to objects
Hi,
I'm new to R and looking for a way to use a variable to reference to an
object.
I'm plotting several graphs on top of each other and want to do this by
a for loop. The field I want to graph have names like a1,a2,a3, ...
I can't figure out how to get this working:
It should look like this:
lines(spectral$Wavelength,paste("spectral$a",j,sep=""),col=j)
but the "paste()" does not seem to work in this context.
Any help?
Kind regards,
Kris
--
------------------------------------------------------------------------
http://perswww.kuleuven.ac.be/~u0027178/VCard/mycard.php?name=krisn
------------------------------------------------------------------------
Minds are like parachutes, they only work when open
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Kris Nackaerts wrote:> > Hi, > > I'm new to R and looking for a way to use a variable to reference to an > object. > > I'm plotting several graphs on top of each other and want to do this by > a for loop. The field I want to graph have names like a1,a2,a3, ... > I can't figure out how to get this working: > > It should look like this: > lines(spectral$Wavelength,paste("spectral$a",j,sep=""),col=j) > > but the "paste()" does not seem to work in this context. > > Any help?1. I suggest to generate a list "a", which can be indexed with a[[j]], so you don't need any sophisticated mechanism to reference to your objects. 2. Answer of your question: Use get(). Uwe Ligges -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- 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 _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
On Fri, 22 Nov 2002, Kris Nackaerts wrote:> Hi, > > I'm new to R and looking for a way to use a variable to reference to an > object. > > I'm plotting several graphs on top of each other and want to do this by > a for loop. The field I want to graph have names like a1,a2,a3, ... > I can't figure out how to get this working: > > It should look like this: > lines(spectral$Wavelength,paste("spectral$a",j,sep=""),col=j) > > but the "paste()" does not seem to work in this context. >No, it wouldn't. That gives you the name of the variable, not the variable. Probably the simplest solution is either lines(spectral$Wavelength, spectral[[paste("a",j,sep="")]],col=j) but there's also lines(spectral$Wavelength,get(paste("spectral$a",j,sep="")),col=j) and various others -thomas -.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
The "get" function is the usual answer to this sort of question, but
is
not right
for this particular case. Actually, a simpler answer works.
lines(spectral$Wavelength, spectral[[ paste("a", j, sep="")
]], col=j)
Using "get" would want to get objects with names like
"spectral$a1"
rather than the "a1" component of "spectral".
Patrick Burns
patrick at burns-stat.com
+44 (0) 208 525 0696
http://www.burns-stat.com/ (new home of S Poetry)
Kris Nackaerts wrote:
> Hi,
>
> I'm new to R and looking for a way to use a variable to reference to
> an object.
>
> I'm plotting several graphs on top of each other and want to do this
> by a for loop. The field I want to graph have names like a1,a2,a3, ...
> I can't figure out how to get this working:
>
> It should look like this:
>
lines(spectral$Wavelength,paste("spectral$a",j,sep=""),col=j)
>
> but the "paste()" does not seem to work in this context.
>
> Any help?
>
> Kind regards,
>
> Kris
>
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Send "info", "help", or "[un]subscribe"
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