[R] storing element number of a list in a column data frame

[Massimo Bressan]

the list I'm dealing with is the follow-up of an lapply() not a "native" 
data structure I've been set up for storing data originally;
the list it's a data structure I have to manage as a consequence of my 
previous operations, something like:
path<-"./"
files <-list.files(path, pattern=".csv")
mylist<-lapply(files, function(files) 
na.omit(read.csv(paste0(path,"/",files)), header=TRUE))

anyway, thank you for the good hint: is.null seems promising
cheers
m


Il 03/10/2013 16:55, Bert Gunter ha scritto:
> Have you read An Introduction to R (ships with R) or another of the
> many excellent R tutorials on the web? I ask, because you do not
> appear to be using a sensible data structure. As your list appears to
> be of a single type (probably numeric, maybe integer), it would be
> preferable to use a vector, like this:
>
> y <- c(45, NA, 18, NA, 99)
>
> (The NULLS must be converted to NA's to "hold" their places).
>
> There would then seem to be little need for the data frame structure,
> as it tends to slow things down in R. But if you insist,
>
> which(is.na(y))
>
> will give you the indices of the NA's.
>
> See also: ?is.na  ?is.null.
>
>
> Cheers,
> Bert
>
>
>
> On Thu, Oct 3, 2013 at 7:41 AM, Massimo Bressan<mbressan at arpa.veneto.it>  wrote:
>> #let's suppose I have a list like this
>>
>> mytest<-list(45, NULL, 18, NULL, 99)
>>
>> #to note that this is just an amended example because in fact
>>
>> #I'm dealing with a long list (more than 400 elements)
>>
>> #with no evident pattern of the NULL values
>>
>> #I want to end up with a data frame like the following
>>
>> data.frame(i=c(1,3,5), n=c(45,18,99))
>>
>> #i.e. a data frame storing in
>>
>> #column i the number of corresponding element list
>>
>> #column n the unique component of that element
>>
>> #I've been trying with
>>
>> do.call(rbind, mytest)
>>
>> #or
>>
>> do.call(rbind.data.frame, mytest)
>>
>> #but this approach is not properly achieving the desired result
>>
>> #now I'm in trouble on how to store each element number of the list in
>> the first column data frame
>>
>> #any help for this?
>>
>> #thanks
>>
>>
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>>
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