This is definitely not an error, all these behaviours are by design. You need
to (re)read the description of factors in the Introduction to R document that
comes with the software. Factors are not "optimized versions of strings", they
are finite sets of category information designed for use in statistical models.
From this perspective most of the operations you are attempting are nonsensical
because each factor has a unique range of possibilities. If you don't know all
of the possibilities when you read just one data frame then you should be using
the stringsAsFactors=FALSE argument to the function you are creating the data
frame with. Only when you have assembled all of your data into one data frame
and are ready to reference categorical variables in a formula or plot should
you convert your strings to factors.
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On March 30, 2014 3:58:22 AM PDT, Frank Schwidom <schwi...@gmx.net> wrote:
>Hi,
>
>> c( factor( 'a'), ( 1))
>[1] 1 1
>> c( factor( 'a'), factor( 1))
>[1] 1 1
>> c( factor( 'a'), factor( 'b'))
>[1] 1 1
>
>> unlist( list( factor( 'a'), 1))
>[1] 1 1
>
>> unlist( list( factor( 'a'), factor( 1)))
>[1] a 1
>Levels: a 1
>
>> unlist( list( factor( 'a'), factor( 'b')))
>[1] a b
>Levels: a b
>
>
>In an data.frame it is the same
>
>> unlist( data.frame( factor( 'a'), factor( 1)))
>factor..a.. factor.1.
> a 1
>Levels: a 1
>> unlist( data.frame( factor( 'a'), ( 1)))
>factor..a.. X.1.
> 1 1
>
>Im not sure, whether this behaviour can be
>seen as an error. But if I for instance use
>
>read.table or scan then these functions
>will use data.frame(...,
># with
> stringsAsFactors = default.stringsAsFactors())
>
>And so rows will by default appear, which
>contains factors and numbers.
>
>If i want to convert the content in an
>as.character datatype then the factor indexes
>will be used instead of the strings.
>
>This behaviour changes, if i switch off
>the global Option
>
>options( stringsAsFactors= FALSE)
>
>> unlist( data.frame( 'a', ( 1)))
>X.a. X.1.
>
>> unlist( list( 'a', ( 1)))
>[1] "a" "1"
>
>
>This leads to some questions:
>
>If factors represent an
>optimized vector of strings (or other datatypes)
>why can an operation on this factor not behave
>like an operation on vector of strings (or ...)?
>
>And: what is the best solution to convert an
>list( factor, number) to its character representation?
>
>Or: is it a bug?
>
>Regards
>
>______________________________________________
>R-help@r-project.org mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide
>http://www.R-project.org/posting-guide.html
>and provide commented, minimal, self-contained, reproducible code.
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