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problem with using apply for dataframe
4 messages · Jessica Streicher, Eik Vettorazzi, Marion Wenty
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Hi Marion, as stated in the help file ?apply coerces a data.frame object into an array. Since an array has only one type of data, this coercion turns all your variables into strings (because this data type can hold all information given without loss). If it happens that your data.frame consists only of numeric variables, then this type suffices for the array as well, and things like sum or mean can be applied row/columnwise. btw: apply(mydataframe,2,function(x)sum(x)) doesn't work either (for the same reason). Cheers Am 19.07.2012 11:48, schrieb Marion Wenty:
Dear people,
I am including an example of a dataframe:
mydataframe<-data.frame(X=c(1:4),total_bill=c(16.99,10.34,21.01,23.68),tip=c(1.01,1.66,3.50,3.31),sex=c("Male","Male","Male","Female"))
When I use the sapply function getting the information about the factors
works:
sapply(mydataframe,function(x)is.factor(x))
X total_bill tip sex
FALSE FALSE FALSE TRUE
But if I use the apply function it doesn't work:
apply(mydataframe,2,function(x)is.factor(x))
X total_bill tip sex
FALSE FALSE FALSE FALSE
I don't understand why, because I have used the apply function for
dataframes before e.g. using sum(x) instead of is.factor(x) and it did work.
Could anyone help me with this?
Thank you very much for your help in advance!
Marion
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Eik Vettorazzi Department of Medical Biometry and Epidemiology University Medical Center Hamburg-Eppendorf Martinistr. 52 20246 Hamburg T ++49/40/7410-58243 F ++49/40/7410-57790 -- Pflichtangaben gem?? Gesetz ?ber elektronische Handelsregister und Genossenschaftsregister sowie das Unternehmensregister (EHUG): Universit?tsklinikum Hamburg-Eppendorf; K?rperschaft des ?ffentlichen Rechts; Gerichtsstand: Hamburg Vorstandsmitglieder: Prof. Dr. Guido Sauter (Vertreter des Vorsitzenden), Dr. Alexander Kirstein, Joachim Pr?l?, Prof. Dr. Dr. Uwe Koch-Gromus
4 days later
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