[R] Extracting elements out of list in list in list

[Rainer M Krug]

Chel Hee Lee <chl948 at mail.usask.ca> writes:

> This approach may not be fancy as what you are looking for.

As long as it works ans=d it is efficient, it is OK.

>
>> xl <- unlist(x)

The unlist might be a problem as I am working with quite large lists.

>> xl[grep("A", names(xl))]

The grep has one problem, as it would also return fields which contain
an "A", e.g. "Alpha". I am sure this could be fixed with a regular
expression.


> f1.x1.A f1.x2.A f2.x3.A f2.x4.A
>      11      12      13      14
>>
>
> I hope this helps.

Thanks,

Rainer.

>
> Chel Hee Lee
>
> On 01/16/2015 04:40 AM, Rainer M Krug wrote:
>> Hi
>>
>> Consider the following variable:
>>
>> --8<---------------cut here---------------start------------->8---
>> x1 <- list(
>>    A = 11,
>>    B = 21,
>>    C = 31
>> )
>>
>> x2 <- list(
>>    A = 12,
>>    B = 22,
>>    C = 32
>> )
>>
>> x3 <- list(
>>    A = 13,
>>    B = 23,
>>    C = 33
>> )
>>
>> x4 <- list(
>>    A = 14,
>>    B = 24,
>>    C = 34
>> )
>>
>> y1 <- list(
>>    x1 = x1,
>>    x2 = x2
>> )
>>
>> y2 <- list(
>>    x3 = x3,
>>    x4 = x4
>> )
>>
>> x <- list(
>>    f1 = y1,
>>    f2 = y2
>> )
>> --8<---------------cut here---------------end--------------->8---
>>
>>
>> To extract all fields named "A" from y1, I can do
>>
>> ,----
>> | > sapply(y1, "[[", "A")
>> | x1 x2
>> | 11 12
>> `----
>>
>> But how can I do the same for x?
>>
>> I could put an sapply into an sapply, but this would be less then
>> elegant.
>>
>> Is there an easier way of doing this?
>>
>> Thanks,
>>
>> Rainer
>>
>>
>>
>> ______________________________________________
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>> and provide commented, minimal, self-contained, reproducible code.
>>
>

-- 
Rainer M. Krug
email: Rainer<at>krugs<dot>de
PGP: 0x0F52F982
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