lol. you´re right, the " " is special.
On 29.04.2010, at 18:34, David Winsemius wrote:
> That was copied from the help page the comes up with:
>
> ?"$"
>
> It is rather "special".
>
> -- David.
>
> On Apr 29, 2010, at 12:26 PM, Bunny, lautloscrew.com wrote:
>
>> Nice, thx. Which manual do you use ? an introduction to R ? Or something
>> special ?
>>
>> matt
>>
>>
>> On 29.04.2010, at 15:25, David Winsemius wrote:
>>
>>>
>>> On Apr 29, 2010, at 9:03 AM, Bunny, lautloscrew.com wrote:
>>>
>>>> Sorry for that offlist post, did not mean to do it intentionally. just hit
>>>> the wrong button. Unfortunately this disadvantage is not written next to $
>>>> in the manual.
>>>
>>> Hmmm. Not my manual:
>>>
>>> "Both [[ and $ select a single element of the list. The main difference is
>>> that $ does not allow computed indices, whereas [[does."
>>>
>>>
>>> It also says that the correct equivalent using extraction operators of "$"
>>> would be:
>>>
>>> x$name == x[["name", exact = FALSE]]
>>> --
>>> David.
>>>>
>>>>
>>>>>
>>>>> On Apr 29, 2010, at 2:34 AM, Bunny, lautloscrew.com wrote:
>>>>>
>>>>>> David,
>>>>>>
>>>>>> With your help i finally got it. THX!
>>>>>> sorry for handing out some ugly names.
>>>>>> Reason being: it´s a german dataset with german variable names. With
>>>>>> those german names you are always sure you dont use a forbidden
>>>>>> name. I just did not want to hit one of those by accident when changing
>>>>>> these names for the mailing list. columna is just the latin term for
>>>>>> column :) . Anyway here´s what worked
>>>>>>
>>>>>> note: I just tried to use some more "real" names here.
>>>>>>
>>>>>> recode_items = function(dataframe,question_number,medium=3){
>>>>>>
>>>>>> #note column names of the initial data.frame are like
>>>>>> Question1,Question2 etc. Using [,1] would not be very practical since
>>>>>> # the df contains some other data too. Indexing by names seemed
>>>>>> to most comfortable way so far.
>>>>>> question<-paste("Question",question_number,sep="")
>>>>>> # needed indexing here that understands characters, that´s why
>>>>>> going with [,question_number] did not work.
>>>>>> dataframe[question][dataframe[question]==3]=0
>>>>>
>>>>> This would be more typical:
>>>>>
>>>>> dataframe[dataframe[question]==3, question] <- 0
>>>>>
>>>>>>
>>>>>>
>>>>>> return(dataframe)
>>>>>>
>>>>>> }
>>>>>>
>>>>>> recode_items(mydataframe,question_number,3)
>>>>>> # this call uses the dataframe that contains the answers of survey
>>>>>> participants. Question number is an argument that selects the question
>>>>>> from the dataframe that should be recoded. In surveys some weighting
>>>>>> schemes only respect extreme answers, which is why the medium answer is
>>>>>> recoded to zero. Since it depends on the item scale what medium actually
>>>>>> is, I need it to be an argument of my function.
>>>>>>
>>>>>>> Did you want a further logical test with that "=1" or some sort of
>>>>>>> assignment???
>>>>>>
>>>>>> So yes, it´s an assignment.
>>>>>>
>>>>>>>> Moral: Generally better to use "[" indexing.
>>>>>>
>>>>>> That´s what really made my day (and it´s only 9.30 a.m. here ) . Are
>>>>>> there exceptions to rule?
>>>>>
>>>>> Not that I know of.
>>>>>
>>>>>> I just worked a lot with the $ in the past.
>>>>>
>>>>> "$colname" is just syntactic sugar for either "["colname"]" or "[
>>>>> ,"colname"]" and it has the disadvantage that colname is not evaluated.
>>>>>
>>>>>
>>>>>>
>>>>>> thx
>>>>>>
>>>>>> matt
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On 29.04.2010, at 00:56, David Winsemius wrote:
>>>>>>
>>>>>>>
>>>>>>> On Apr 28, 2010, at 5:45 PM, David Winsemius wrote:
>>>>>>>
>>>>>>>>
>>>>>>>> On Apr 28, 2010, at 5:31 PM, Bunny, lautloscrew.com wrote:
>>>>>>>>
>>>>>>>>> Dear all,
>>>>>>>>>
>>>>>>>>> i have a problem with processing dataframes within a function using
>>>>>>>>> the "$".
>>>>>>>>> Here´s my code:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> recode_items = function(dataframe,number,medium=2){
>>>>>>>>>
>>>>>>>>> # this works
>>>>>>>>> q<-paste("columna",number,sep="")
>>>>>>>>
>>>>>>>> Do your really want q to equal "columna2" when "number" equals 2?
>>>>>>>>
>>>>>>>>>
>>>>>>>>> # this does not work, particularly because "dataframe" is not
>>>>>>>>> processed
>>>>>>>>> # dataframe should be: givenframe$columnagivennumber
>>>>>>>>> a=dataframe$q[dataframe$q==medium]=1
>>>>>>>
>>>>>>> Did you want a further logical test with that "=1" or some sort of
>>>>>>> assignment???
>>>>>>>
>>>>>>>>
>>>>>>>> a) Do you want to work on the column from dataframe ( horrible name
>>>>>>>> for this purpose IMO) with the name "columna2"? If so, then start with
>>>>>>>>
>>>>>>>> dataframe[ , q ]
>>>>>>>>
>>>>>>>> .... the "q" will be evaluated in this form whereas it would not when
>>>>>>>> used with "$".
>>>>>>>>
>>>>>>>> b) (A guess in absence of explanation of a goal.) Now do you want all
>>>>>>>> of the rows where that vector equals "medium"? If so ,then try this:
>>>>>>>>
>>>>>>>> dataframe[ dataframe[ , q ]==2 , ] # untested in the absence of data
>>>>>>>
>>>>>>> Ooops. should have been:
>>>>>>>
>>>>>>> dataframe[ dataframe[ , q ]==medium , ] #since both q and medium will
>>>>>>> be evaluated.
>>>>>>>
>>>>>>>
>>>>>>>>
>>>>>>>> Moral: Generally better to use "[" indexing.
>>>>>>>>
>>>>>>>> --
>>>>>>>> David.
>>>>>>>>
>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> return(a)
>>>>>>>>>
>>>>>>>>> }
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> If I call this function, i´d like it to return my dataframe. The
>>>>>>>>> problem appears to be somewhere around the $. I´m sure this not too
>>>>>>>>> hard, but somehow i am stuck. I´ll keep searchin the manuals.
>>>>>>>>> Thx for any help in advance.
>>>>>>>>>
>>>>>>>>> best
>>>>>>>>>
>>>>>>>>> matt
>>>>>>>>> [[alternative HTML version deleted]]
>>>>>>>>>
>>>>>>>>> ______________________________________________
>>>>>>>>> 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.
>>>>>>>>
>>>>>>>> ______________________________________________
>>>>>>>> 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.
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>> David Winsemius, MD
>>> West Hartford, CT
>>>
>>
>
> David Winsemius, MD
> West Hartford, CT
>
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