R - apply function to data frames serially

Question

I have dataframe mydf and I've split it to get number of data frames like mydf$'1' mydf$'2'...mydf$'n'. I wish to apply my function on these data frames to get resultdf like

resultdf1 <- myfunc(mydf$'1')
resultdf2 <- myfunc(mydf$'2')
.....
resultdfn <- myfunc(mydf$'n')

and so on...Since there are about 35 data frames from the split. How can I reduce my effort without manually writing for each frame name and resultdf.

I tried lapply but didn't work out correctly. Any help will be appreciated.

Thanks

What didn't work out correctly? Please show what you tried and the output. — Tim Biegeleisen, Aug 25 '16 at 04:45
Don't have sequentially named variables - [use a list of data frames](http://stackoverflow.com/a/24376207/903061). — Gregor Thomas, Aug 25 '16 at 04:54

Tim Biegeleisen · Accepted Answer · 2016-08-25T04:51:58.750

3

Calling split on a data frame should give you a list of smaller data frames. So perhaps it would just make sense to call lapply on this split list, e.g.

mydf.split <- split(mydf, mydf$col)
list.result <- lapply(mydf.split, function(x) { /* do something */ })

The above would yield another list, with each node containing the result of your function. If you want to get back a vector instead, you could use sapply. For example, if you wanted the number of rows in each of your split data frames, you could do

mydf.counts <- sapply(mydf.split, function(x) nrow(x))

edited Aug 25 '16 at 04:51

answered Aug 25 '16 at 04:43

Tim Biegeleisen

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And after that you can bind.rows from dplyr on list to get 1 data frame. – M. Siwik Aug 25 '16 at 04:50
1

@M.Siwik if you're using `dplyr`, why would you even split in the first place? Just `group_by`... – Gregor Thomas Aug 25 '16 at 04:53
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Sometimes it's easier to write something as function in lapply on list of dataframes than using group_by for me;) – M. Siwik Aug 25 '16 at 04:58
This was good...I was overly concerned with naming in the split frame and result frame. – Tarak Aug 25 '16 at 05:08

R - apply function to data frames serially

1 Answers1