[R] exists function on list objects gives always a FALSE

[Romain Francois]

Žroutík wrote:
> Dear R-users,
>
> in a minimal example exists() gives FALSE on an object which obviously does
> exist. How can I check on that list object anyway else, please?
>
>   
>> SmoothData <- list(exists=TRUE, span=0.001)
>> SmoothData
>>     
> $exists
> [1] TRUE
>
> $span
> [1] 0.001
>
>   
>> exists("SmoothData")
>>     
> TRUE
>   
>> exists("SmoothData$span")
>>     
> FALSE
>   
This checks for existance of an object called "SmoothData$span", as in :

`SmoothData$span` <- 1:10
exists("SmoothData$span")

You can do:

is.list( SmoothData ) && !is.null(names(SmoothData)) && "span" %in% 
names(SmoothData)

>   
>> exists("SmoothData[[2]]")
>>     
> FALSE
>   
Similarly:

`SmoothData[[2]]` <- 1
exists("SmoothData[[2]]")

You can do:

is.list( SmoothData ) && length(SmoothData) > 1

> Thank you for any opinion regarding this topic.
> Zroutik


-- 
Romain Francois
Independent R Consultant
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr