# [R] How to split two levels several times?

Wed Jul 24 23:47:07 CEST 2013

```Hello,

As for the first question, note that in the case you describe, the
resulting list of df's will not be a split of the original, there will
be a duplication in the final 4-1 and 1-3. The following is a hack but
will do it.

lens <- rle(as.character(XXX\$electrode))\$lengths
m <- length(lens) %/% 2
idx <- rep(1:m, sapply(1:m, function(.m) sum(lens[(2*.m - 1):(2*.m)])))
if(length(lens) %% 2 != 0)
idx <- c(idx, rep(m + 1, lens[length(lens)]))

sp <- split(XXX, idx)

if(length(lens) %% 2 != 0){
idx2 <- sp[[m]]\$electrode == sp[[m]]\$electrode[nrow(sp[[m]])]
sp[[m + 1]] <- rbind(sp[[m]][idx2, ], sp[[m + 1]])
}
sp

As for the second question, I'm not understanding it, can you post
sample output?

Em 24-07-2013 13:58, dennis1991 at gmx.net escreveu:
> Hi Rui
> the splitting code worked fine. Thanks for your help. Now I realized that the code cannot handle a table with levels that by chance (or systematically) repeatedly appear after each other. For instance this may happen if I need to extract the final two pairs of the table XXX below: electrode4+electrode1 and electrode1+electrode3.
>
> lens <- rle(as.character(XXX\$electrode))\$lengths
> will return 3 2 3 2 6 6 3 and not 3 2 3 2 6 3 3 3 because it counts electrode1 double.
> split(XXX, idx) will produce 3 incorrect outputs instead of the required 4.
> This will also occur if I have systematic combinations 1-4 after each other for instance in a new table “XX” below where electrode4 appears twice.
>
> Is there a way to make splitting "half-way" between two of the same levels possible by predefining the length of each individual level? This would make the splitting code more robust. Thanks for advice.
>
>
> This is the table "XXX"
>
> electrode length
>
> electrode1 5.7
> electrode1 6.3
> electrode1 6.2
> electrode2 11.4
> electrode2 9.7
> electrode3 14.2
> electrode3 14.8
> electrode3 12.6
> electrode2 11.4
> electrode2 9.7
> electrode4 17.0
> electrode4 16.3
> electrode4 17.8
> electrode4 18.3
> electrode4 16.9
> electrode4 18.5
> electrode1 5.7
> electrode1 6.3
> electrode1 6.2
> electrode1 5.7
> electrode1 6.3
> electrode1 6.2
> electrode3 14.2
> electrode3 14.8
> electrode3 12.6
>
>
> This is a simplified table XX
>
> electrode1
> electrode2
> electrode1
> electrode3
> electrode1
> electrode4
> electrode2
> electrode1
> electrode2
> electrode3
> electrode2
> electrode4
> electrode3
> electrode1
> electrode3
> electrode2
> electrode3
> electrode4
> electrode4
> electrode1
> electrode4
> electrode2
> electrode4
> electrode3
>
>
>
>
>
>
>> Gesendet: Dienstag, 23. Juli 2013 um 13:36 Uhr
>> An: dennis1991 at gmx.net
>> Cc: smartpink111 at yahoo.com, 'r-help' <r-help at r-project.org>
>> Betreff: Re: Aw: Re: [R] How to split two levels several times?
>>
>> Hello,
>>
>> It's better if you keep this on the list, the odds of getting more and
>>
>> As for your new question, try the following.
>>
>>
>> lens <- rle(as.character(XXX\$electrode))\$lengths
>> m <- length(lens) %/% 2
>> idx <- rep(1:m, sapply(1:m, function(.m) sum(lens[(2*.m - 1):(2*.m)])))
>> split(XXX, idx)
>>
>>
>> Hope this helps,
>>
>>
>> Em 23-07-2013 11:41, dennis1991 at gmx.net escreveu:
>>> Hi
>>> this type of splitting works for my specific example. Thanks for your help.
>>>
>>> I was not absolutely clear what I generally want. I'm looking for an option that generally permits splitting two joint levels of a table after each other. For instance for the table below I want it to be divided into combinations electrode1-electrode2,  electrode3-electrode2,  electrode4-electrode1. How should I split this?
>>>
>>>
>>> This is the table "XXX"
>>>
>>> electrode length
>>>
>>> electrode1 5.7
>>> electrode1 6.3
>>> electrode1 6.2
>>> electrode2 11.4
>>> electrode2 9.7
>>> electrode3 14.2
>>> electrode3 14.8
>>> electrode3 12.6
>>> electrode2 11.4
>>> electrode2 9.7
>>> electrode4 17.0
>>> electrode4 16.3
>>> electrode4 17.8
>>> electrode4 18.3
>>> electrode4 16.9
>>> electrode4 18.5
>>> electrode1 5.7
>>> electrode1 6.3
>>> electrode1 6.2
>>>
>>>
>>>
>>>
>>>
>>>> Gesendet: Montag, 22. Juli 2013 um 17:53 Uhr
>>>> An: dennis1991 at gmx.net
>>>> Cc: r-help at r-project.org
>>>> Betreff: Re: [R] How to split two levels several times?
>>>>
>>>> Hello,
>>>>
>>>> Sorry, I've just realized that your data frame is named 'XXX', not
>>>> 'dat'. Change that and the rest should work:
>>>>
>>>>
>>>> idx <- cumsum(c(TRUE, diff(XXX\$electrode == "electrode1") > 0))
>>>> split(XXX, idx)
>>>>
>>>>
>>>>
>>>> Em 22-07-2013 16:47, Rui Barradas escreveu:
>>>>> Hello,
>>>>>
>>>>> Try the following.
>>>>>
>>>>>
>>>>> idx <- cumsum(c(TRUE, diff(dat\$electrode == "electrode1") > 0))
>>>>> split(dat, idx)
>>>>>
>>>>>
>>>>> Hope this helps,
>>>>>
>>>>>
>>>>> Em 22-07-2013 15:09, dennis1991 at gmx.net escreveu:
>>>>>> Hi,
>>>>>>
>>>>>> I have a small problem with the function split() and would appreciate
>>>>>>
>>>>>> I have a table called “XXX” with 2 columns and 49 rows. The 49 rows
>>>>>> belong to 8 different levels (electrode1, ...,electrode8). I want to
>>>>>> split the table always at the row where “electrode1” starts again so
>>>>>> that I can export 7  individual dataframes (numbered “dataframe1” to
>>>>>> ”dataframe7”) which contain always electrode1 as first level (always
>>>>>> three rows) with the varying number of rows for electrodes2-8 below.
>>>>>> I tried the split function with various setups:
>>>>>>
>>>>>> t <- as.factor(XXX\$electrode)
>>>>>>
>>>>>> dataframeX <- split(XXX, f=(levels=t))
>>>>>>
>>>>>>
>>>>>>
>>>>>> This is the table "XXX"
>>>>>>
>>>>>> electrode    length
>>>>>>
>>>>>> electrode1    5.7
>>>>>> electrode1    6.3
>>>>>> electrode1    6.2
>>>>>> electrode2    11.4
>>>>>> electrode2    9.7
>>>>>> electrode1    5.7
>>>>>> electrode1    6.3
>>>>>> electrode1    6.2
>>>>>> electrode3    14.2
>>>>>> electrode3    14.8
>>>>>> electrode3    12.6
>>>>>> electrode1    5.7
>>>>>> electrode1    6.3
>>>>>> electrode1    6.2
>>>>>> electrode4    17.0
>>>>>> electrode4    16.3
>>>>>> electrode4    17.8
>>>>>> electrode4    18.3
>>>>>> electrode4    16.9
>>>>>> electrode4    18.5
>>>>>> electrode1    ....
>>>>>> ....        ....
>>>>>> electrode5    ....
>>>>>> ....        ....
>>>>>> electrode1    ....
>>>>>> electrode6    ....
>>>>>> electrode1    ....
>>>>>> electrode7    ....
>>>>>> electrode1    ....
>>>>>> electrode8    ....
>>>>>>
>>>>>> ______________________________________________
>>>>>> R-help at r-project.org mailing list
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>>>>>> and provide commented, minimal, self-contained, reproducible code.
>>>>>>
>>>>>
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