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
>
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