R help - Aug 2014 - find the data frames in list of objects and make a list of them

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

Here is a function that I use that might give you the results you want:

================> my.ls()
                       Size      Class  Length         Dim
.Random.seed          2,544    integer     626
.remapHeaderFile     40,440 data.frame       2     373 x 2
colID                   216  character       3
delDate                 104  character       1
deliv                15,752 data.table       7     164 x 7
f_drawPallet         36,896   function       1
i                        96  character       1
indx                168,816  character    1782
pallet              172,696 data.table       3    1782 x 3
pallets             405,736 data.table      14   1782 x 14
picks            26,572,856 data.table      19 154247 x 19
wb                      656   Workbook       1
wSplit           68,043,136       list    1782
x                        56    numeric       2
**Total          95,460,000    ------- -------     -------

===================> my.ls
function (pos = 1, sorted = FALSE, envir = as.environment(pos))
{
    .result <- sapply(ls(envir = envir, all.names = TRUE),
function(..x) object.size(eval(as.symbol(..x),
        envir = envir)))
    if (length(.result) == 0)
        return("No objects to list")
    if (sorted) {
        .result <- rev(sort(.result))
    }
    .ls <- as.data.frame(rbind(as.matrix(.result), `**Total` = sum(.result)))
    names(.ls) <- "Size"
    .ls$Size <- formatC(.ls$Size, big.mark = ",", digits = 0,
        format = "f")
    .ls$Class <- c(unlist(lapply(rownames(.ls)[-nrow(.ls)],
function(x) class(eval(as.symbol(x),
        envir = envir))[1L])), "-------")
    .ls$Length <- c(unlist(lapply(rownames(.ls)[-nrow(.ls)],
        function(x) length(eval(as.symbol(x), envir = envir)))),
        "-------")
    .ls$Dim <- c(unlist(lapply(rownames(.ls)[-nrow(.ls)], function(x)
paste(dim(eval(as.symbol(x),
        envir = envir)), collapse = " x "))), "-------")
    .ls
}
=======================
Jim Holtman
Data Munger Guru

What is the problem that you are trying to solve?
Tell me what you want to do, not how you want to do it.


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
>
> ______________________________________________
> 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.

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
>
> ______________________________________________
> 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.