Dear Paulo, Your object is a named vector. Apply() and colMeans() only work on matrices and dataframes. So you need to convert the vector to a matrix or data.frame. See the example below. Please not that calculating the mean of one element is a waiste of time.
# a named numerical vector object <- c(x = 670, y = 314) str(object) class(object) #a data frame with two numerical vectors. object2 <- data.frame(x = 670, y = 314) str(object2) class(object2) colMeans(object2) HTH, Thierry ------------------------------------------------------------------------ ---- ir. Thierry Onkelinx Instituut voor natuur- en bosonderzoek / Research Institute for Nature and Forest Cel biometrie, methodologie en kwaliteitszorg / Section biometrics, methodology and quality assurance Gaverstraat 4 9500 Geraardsbergen Belgium tel. + 32 54/436 185 thierry.onkel...@inbo.be www.inbo.be To call in the statistician after the experiment is done may be no more than asking him to perform a post-mortem examination: he may be able to say what the experiment died of. ~ Sir Ronald Aylmer Fisher The plural of anecdote is not data. ~ Roger Brinner The combination of some data and an aching desire for an answer does not ensure that a reasonable answer can be extracted from a given body of data. ~ John Tukey -----Oorspronkelijk bericht----- Van: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] Namens Paulo Eduardo Cardoso Verzonden: maandag 3 augustus 2009 16:19 Aan: David Winsemius CC: [R] Onderwerp: Re: [R] apply function to named numeric object Both objects are numeric, but they differ in structure and I don't know how to handle both with a single function to get means. When I try to apply colMeans to a named numeric object like this: Named num [1:2] 670 314 - attr(*, "names")= chr [1:2] "x" "y" I get the error messages: Error in colMeans(centroid) : 'x' must be an array of at least two dimensions and apply(object,2,mean) Error in apply(object, 2, mean) : dim(X) must have a positive length There are something very basic that I'm missing. 2009/8/3 David Winsemius <dwinsem...@comcast.net> > > On Aug 3, 2009, at 9:52 AM, Paulo Eduardo Cardoso wrote: > > Thanks. Works > A doubt. > > I asked that because I have a loop that can generate objects like that > or this one > > > str(object) > Named num [1:2] 670 314 > - attr(*, "names")= chr [1:2] "x" "y" > > To avoid using a ifelse() to calculate means of x and y, I'd like a > function that handle with this named numeric object and that list. Any > chance of do it with a single function? > > > I do not see any list object. Lists and arrays (of which the two > dimensional ones are of type "matrix") are quite different basic data > structures in R. If you interchange the use of those terms you will > not get useful replies from R users. Those two object both appear to > be matrices and both should be handled by those functions. > > > 2009/8/3 David Winsemius <dwinsem...@comcast.net> > >> >> On Aug 3, 2009, at 9:07 AM, Paulo Eduardo Cardoso wrote: >> >> Maybe a very basic question. >>> How can I get mean of a object like this >>> >>> str(object) >>>> >>> num [1:53, 1:2] 734 734 736 734 736 ... >>> - attr(*, "dimnames")=List of 2 >>> ..$ : NULL >>> ..$ : chr [1:2] "x" "y" >>> >>> I want the mean of both x and y >>> >> >> apply(object, 2, mean) >> >> or... >> >> colMeans(object) # which will be faster >> >> >> _______________ >>> Paulo E. Cardoso >>> >>> [[alternative HTML version deleted]] >>> >>> __________________________________________ >>> >> > > David Winsemius, MD > Heritage Laboratories > West Hartford, CT > > -- _______________ Paulo E. Cardoso [[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. Dit bericht en eventuele bijlagen geven enkel de visie van de schrijver weer en binden het INBO onder geen enkel beding, zolang dit bericht niet bevestigd is door een geldig ondertekend document. The views expressed in this message and any annex are purely those of the writer and may not be regarded as stating an official position of INBO, as long as the message is not confirmed by a duly signed document. ______________________________________________ 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.
