# [R] How to get a specific named element in a nested list

Friedericksen Hope friedericksen.hope at gmail.com
Thu Nov 11 10:27:09 CET 2010

```Hi Ivan,

thank you very much for your detailed explanations and response!
Please excuse, that I did not include a reproducible example.

Yes, what I am looking for is such a function - but I suspect, that it does not exist already, so I have to write it on my own.

Best,
Friedericksen

On 11/11/2010 10:23 AM, Ivan Calandra wrote:
> Hi,
>
> A reproducible example would have been nice, but a correct code even more (you forgot some commas)!
>
> So if you meant this:
> x <- list(
> list(
> list(df1,df2),
> list(df3,
> list(df4,df5)),
> list(df6,df7)))
>
> check str(x): (I removes the details of each df)
> List of 1
> \$ :List of 3
> ..\$ :List of 2
> .. ..\$ :'data.frame': 10 obs. of 2 variables: ## df1
> .. ..\$ :'data.frame': 10 obs. of 2 variables: ## df2
> ..\$ :List of 2
> .. ..\$ :'data.frame': 10 obs. of 2 variables: ## df3
> .. ..\$ :List of 2
> .. .. ..\$ :'data.frame': 10 obs. of 2 variables: ## df4
> .. .. ..\$ :'data.frame': 10 obs. of 2 variables: ## df5
> ..\$ :List of 2
> .. ..\$ :'data.frame': 10 obs. of 2 variables: ## df6
> .. ..\$ :'data.frame': 10 obs. of 2 variables: ## df7
>
> And check x: (I removed the details again)
> [[1]]
> [[1]][[1]]
> [[1]][[1]][[1]]
> df1
> [[1]][[1]][[2]]
> df2
>
> [[1]][[2]]
> [[1]][[2]][[1]]
> df3
> [[1]][[2]][[2]]
> [[1]][[2]][[2]][[1]]
> df4
> [[1]][[2]][[2]][[2]]
> df5
>
> [[1]][[3]]
> [[1]][[3]][[1]]
> df6
> [[1]][[3]][[2]]
> df7
>
> If you want to access them, you need to follow the structure of your list, e.g.
> for df1:
> x[[1]][[1]][[1]]
> for df5:
> x[[1]][[2]][[2]][[2]]
>
> You need to access them with indexes because the list elements are unnamed.
> Now if you do:
> x <- list(uppermost=list(
> medium1=list(df1=df1,df2=df2),
> medium2=list(df3=df3,
> lowermost=list(df4=df4,df5=df5)),
> medium3=list(df6=df6,df7=df7)))
>
> You can access them with names (but you still need to follow the structure, i.e. x[[df5]] cannot work):
> For df1:
> x\$uppermost\$medium1\$df1 or x[["uppermost"]][["medium1"]][["df1"]]
> for df5:
> x\$uppermost\$medium2\$lowermost\$df5 or x[["uppermost"]][["medium2"]][["lowermost"]][["df5"]]
>
>
> But I guess you can write a function that would "search" through the structure of x for a given df (that has to be named then) and return it.
> Maybe you have your reasons to have such a complicated list, but if it were me, I would make it easier to understand and to access (i.e. less nested, max 2 levels)
>
> HTH,
> Ivan
>
>
>
>
> Le 11/11/2010 09:05, Friedericksen Hope a écrit :
>> Hello,
>>
>> I have a nested named list structure, like the following:
>>
>> x <- list(
>> list(
>> list(df1,df2)
>> list(df3,
>> list(df4,df5))
>> list(df6,df7)))
>>
>> with df1...d7 as data frames. Every data frame is named.
>>
>> Is there a way to get a specific named element in x?
>>
>> so, for example,
>>
>> x[[c("df5")]] gives me the data frame 5?
>>
>>
>> Best,
>> Friedericksen
>>
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