On 5/19/2009 12:07 PM, 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
exists("SmoothData[[2]]")
FALSE
Thank you for any opinion regarding this topic.
There is no variable with name "SmoothData$span", there is an element of
SmoothData with name "span".
To test for that, the safest test is probably
"span" %in% names(SmoothData)
but a common convention is to use
is.null(SmoothData$span)
because NULL elements are rare in lists.
Duncan Murdoch
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