R help - Oct 2008 - Extracting variables with a given prefix in the parent environment

hi,

get.vars.name.prefix<-function(prefix){
 result<-list()
 len<-nchar(prefix)
 var.names<-ls(name=1,pattern=prefix) #name=1 probably wrong option
 print(var.names)
 for(i in 1:length(var.names)){
  name<-var.names[i]
  field<-substr(name,len+1,nchar(name))
  result[[field]]<-get(name)
 }
 result
}

for example
x.1<-1
x.2<-2
get.vars.name.prefix("x.") should return 1,2

this does not work if i call if from within another function:

g<-function(){
  x.1<-1
  x.2<-2
  get.vars.name.prefix("x.") # should return 1,2, nothing else
}

i would like the environment specified within ls(...) to be that of the body
of the function that calls get.vars.name.prefix. apparently name=1 is
probably not the right option.

thanks.

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On 20/10/2008 2:06 AM, erwann rogard wrote:
> hi,
> 
> get.vars.name.prefix<-function(prefix){
>  result<-list()
>  len<-nchar(prefix)
>  var.names<-ls(name=1,pattern=prefix) #name=1 probably wrong option
>  print(var.names)
>  for(i in 1:length(var.names)){
>   name<-var.names[i]
>   field<-substr(name,len+1,nchar(name))
>   result[[field]]<-get(name)
>  }
>  result
> }
> 
> for example
> x.1<-1
> x.2<-2
> get.vars.name.prefix("x.") should return 1,2
> 
> this does not work if i call if from within another function:
> 
> g<-function(){
>   x.1<-1
>   x.2<-2
>   get.vars.name.prefix("x.") # should return 1,2, nothing else
> }
> 
> i would like the environment specified within ls(...) to be that of the
body
> of the function that calls get.vars.name.prefix. apparently name=1 is
> probably not the right option.
Use ls(name=parent.frame(), pattern=...)

And be careful about the pattern:  it's a regular expression, so you 
would need to start with a caret "^" to guarantee that it occurs at
the
start of the name.

Duncan Murdoch

Try this:

Using 'envir' argument, in ls and get function:

get.vars.name.prefix<-function(prefix, envir = parent.frame()){
   result<-list()
   len<-nchar(prefix)
   var.names<-ls(envir = envir,pattern=prefix)
   print(var.names)
   for(i in 1:length(var.names)){
      name<-var.names[i]
      field<-substr(name,len+1,nchar(name))
      result[[field]]<-get(name, envir = envir)
  }
 result
}

On Mon, Oct 20, 2008 at 4:06 AM, erwann rogard
<erwann.rogard@gmail.com>wrote:
> hi,
>
> get.vars.name.prefix<-function(prefix){
>  result<-list()
>  len<-nchar(prefix)
>  var.names<-ls(name=1,pattern=prefix) #name=1 probably wrong option
>  print(var.names)
>  for(i in 1:length(var.names)){
>  name<-var.names[i]
>  field<-substr(name,len+1,nchar(name))
>  result[[field]]<-get(name)
>  }
>  result
> }
>
> for example
> x.1<-1
> x.2<-2
> get.vars.name.prefix("x.") should return 1,2
>
> this does not work if i call if from within another function:
>
> g<-function(){
>  x.1<-1
>  x.2<-2
>  get.vars.name.prefix("x.") # should return 1,2, nothing else
> }
>
> i would like the environment specified within ls(...) to be that of the
> body
> of the function that calls get.vars.name.prefix. apparently name=1 is
> probably not the right option.
>
> thanks.
>
>        [[alternative HTML version deleted]]
>
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>


-- 
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O

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