[R] Split a dataframe by rownames and/or colnames

[Tim Richter-Heitmann]

Thank you very much for the line. It was doing the split as suggested.
However, i want to release all the dataframes to the environment (later 
on, for each dataframe, some dozen lines of code will be carried out, 
and i dont know how to do it w lapply or for-looping, so i do it 
separately):

list2env(split(df, sub(".+_","", rownames(df))), envir=.GlobalEnv)

Anyway, the dataframes have now numeric names in some cases, and cannot 
be easily accessed because of it.
How would the line be  altered to add an "df_" for each  of the 
dataframe names resulting from list2env?

Thank you very much!



Thanks, On 20.02.2015 20:36, David Winsemius wrote:
> On Feb 20, 2015, at 9:33 AM, Tim Richter-Heitmann wrote:
>
>> Dear List,
>>
>> Consider this example
>>
>> df <- data.frame(matrix(rnorm(9*9), ncol=9))
>> names(df) <- c("c_1", "d_1", "e_1", "a_p", "b_p", "c_p", "1_o1", "2_o1", "3_o1")
>> row.names(df) <- names(df)
>>
>>
>> indx <- gsub(".*_", "", names(df))
>>
>> I can split the dataframe by the index that is given in the column.names after the underscore "_".
>>
>> list2env(
>>   setNames(
>>     lapply(split(colnames(df), indx), function(x) df[x]),
>>     paste('df', sort(unique(indx)), sep="_")),
>>   envir=.GlobalEnv)
>>
>> However, i changed my mind and want to do it now by rownames. Exchanging colnames with rownames does not work, it gives the exact same output (9 rows x 3 columns). I could do
>> as.data.frame(t(df_x),
>> but maybe that is not elegant.
>> What would be the solution for splitting the dataframe by rows?
> The split.data.frame method seems to work perfectly well with a rownames-derived index argument:
>
>> split(df, sub(".+_","", rownames(df) ) )
> $`1`
>        c_1   d_1  e_1   a_p   b_p   c_p  1_o1 2_o1  3_o1
> c_1 -0.11 -0.04 1.33 -0.87 -0.16 -0.25 -0.75 0.34  0.14
> d_1 -0.62 -0.94 0.80 -0.78 -0.70  0.74  0.11 1.44 -0.33
> e_1  0.98 -0.83 0.48  0.19 -0.32 -1.01  1.28 1.04 -2.16
>
> $o1
>         c_1   d_1   e_1   a_p   b_p   c_p  1_o1  2_o1  3_o1
> 1_o1 -0.93 -0.02  0.69 -0.67  1.04  1.04 -1.50 -0.36  0.50
> 2_o1  0.02 -0.16 -0.09 -1.50 -0.02 -1.04  1.07 -0.45  1.56
> 3_o1 -1.42  0.88 -0.05  0.85 -1.35  0.21  1.35  0.92 -0.76
>
> $p
>        c_1   d_1   e_1   a_p  b_p   c_p  1_o1  2_o1  3_o1
> a_p -1.35  0.91 -0.58 -0.63 0.94 -1.13  0.71  0.25  0.82
> b_p -0.25 -0.73 -0.41 -1.71 1.28  0.19 -0.35  1.74 -0.93
> c_p -0.01 -1.11 -0.12  0.58 1.51  0.03 -0.99 -0.23 -0.03
>
>> Thank you very much!
>>
>> -- 
>> Tim Richter-Heitmann
>>


-- 
Tim Richter-Heitmann (M.Sc.)
PhD Candidate



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