[R] Trouble with Paste and Quotes and List Objects

[Sparks, John James]

Dear R Helpers,

I have a list that contains a number of objects, each of them financial
statement data from quantmod (although I don't think that knowledge of
quantmod is necessary to help with this problem).

> str(listfinobj)
 chr [1:4815] "A.f" "AA.f" "AACC.f" "AAME.f" "AAN.f" "AAON.f" "AAP.f"
"AAPL.f" "AAT.f" "AATI.f" "AAU.f" ...

I can easily pick out the 3rd object in this list.
> listfinobj[[3]]
[1] "AACC.f"

Each of the .f objects has a mildly complicated structure (partial results
shown below).
> str(AACC.f)
List of 3
 $ IS:List of 2
  ..$ Q: num [1:49, 1:5] 50.4 NA 50.4 NA 50.4 ...
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : chr [1:49] "Revenue" "Other Revenue, Total" "Total Revenue"
"Cost of Revenue, Total" ...
  .. .. ..$ : chr [1:5] "2011-03-31" "2010-12-31" "2010-09-30"
"2010-06-30" ...
  .. ..- attr(*, "col_desc")= chr [1:5] "3 months ending 2011-03-31" "3
months ending 2010-12-31" "3 months ending 2010-09-30" "3 months ending
2010-06-30" ...
  ..$ A: num [1:49, 1:4] 198 NA 198 NA 198 ...
  .. ..- attr(*, "dimnames")=List of 2
  .. .. ..$ : chr [1:49] "Revenue" "Other Revenue, Total" "Total Revenue"
"Cost of Revenue, Total" ...
  .. .. ..$ : chr [1:4] "2010-12-31" "2009-12-31" "2008-12-31" "2007-12-31"
  .. ..- attr(*, "col_desc")= chr [1:4] "12 months ending 2010-12-31" "12
months ending 2009-12-31" "12 months ending 2008-12-31" "12 months
ending 2007-12-31"
 $ BS:List of 2
  ..$ Q: num [1:42, 1:5] NA NA 6.53 326.25 NA ...
....

I can get the column names for one of the sub-objects of this object.
> colnames(AACC.f$IS$A)
[1] "2010-12-31" "2009-12-31" "2008-12-31" "2007-12-31"

Thanks for your patience so far; here's the question.

I want to get the column names from all the sub objects in each of the .f
objects, so I want to build a loop, but I need to be able to refer to the
column names of the sub object dynamically.  My many attempts with paste
and get have not worked, I believe because of the quotes and the $'s.  For
example

> temp<-colnames(paste(listfinobj[[3]],$BS$A)[1],sep=",")
Error: unexpected '$' in "temp<-colnames(paste(listfinobj[[3]],$"

> as.name(paste(as.name(listfinobj[[3]]),as.name("$BS$A"),sep=""))
`AACC.f$BS$A`
> colnames(as.name(paste(as.name(listfinobj[[3]]),as.name("$BS$A"),sep="")))
NULL
> as.factor(paste(as.name(listfinobj[[3]]),as.name("$BS$A"),sep=""))
[1] AACC.f$BS$A
Levels: AACC.f$BS$A
> colnames(as.factor(paste(as.name(listfinobj[[3]]),as.name("$BS$A"),sep="")))
NULL

Please help me to understand how to refer to the column names in the
sub-objects of the objects in the list dynamically so that I can build a
loop to get at each of them.

Your help would be much appreciated.
--John J. Sparks, Ph.D.