find the data frames in list of objects and make a list of them

Previously you asked

     A second question: is this the best way to make a list
    of data frames without having to manually type c(dataframe1, dataframe2, ...)  ?

If you use 'c' there you will not get a list of data.frames - you will
get a list of all the columns in the data.frame you supplied.  Use
'list' instead of 'c' if you are taking that route.

The *apply functions are helpful  here.  To make list of all
data.frames in an environment you can use the following function,
which takes the environment to search as an argument.

f <- function(envir = globalenv()) {
     tmp <- eapply(envir,
                            all.names=TRUE,
                            FUN=function(obj) if (is.data.frame(obj))
obj else NULL)
     # remove NULL's now
     tmp[!vapply(tmp, is.null, TRUE)]
}

Use is as
   allDataFrames <- f(globalenv()) # or just f()






Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Wed, Aug 13, 2014 at 3:49 PM, Matthew
<mccormack at molbio.mgh.harvard.edu>  wrote:

Hi Richard,

     Thank you very much for your reply and your code.
Your code is doing just what I asked for, but does not seem to be what I
need.

I will need to review some basic R before I can continue.

I am trying to list data frames in order to bind them into 1 single data
frame with something like: dplyr::rbind_all(list of data frames), but when I
try dplyr::rbind_all(lsDataFrame(ls())), I get the error: object at index 1
not a data.frame. So, I am going to have to learn some more about lists in R
before proceding.

Thank you for your help and code.

Matthew





Matthew

On 8/13/2014 3:12 PM, Richard M. Heiberger wrote:

I would do something like this

lsDataFrame <- function(xx=ls()) xx[sapply(xx, function(x)
is.data.frame(get(x)))]
ls("package:datasets")
lsDataFrame(ls("package:datasets"))

On Wed, Aug 13, 2014 at 2:56 PM, Matthew
<mccormack at molbio.mgh.harvard.edu>  wrote:

Hi everyone,

     I would like the find which objects are data frames in all the
objects I
have created ( in other words in what you get when you type: ls()  ),
then I
would like to make a list of these data frames.

Explained in other words; after typing ls(), you get the names of
objects.
Which objects are data frames ?  How to then make a list of these data
frames.

     A second question: is this the best way to make a list of data frames
without having to manually type c(dataframe1, dataframe2, ...)  ?

Matthew