> Therefore, I would like to know if there are other types of variables > (besides factors) which give a misunderstandable answer about > the type > of their values when asked typeof.
Your question is a bit combative, don't you think? R performs as documented, so I think your characterization is inaccurate and certainly unfair, as software is not required to do what one expects, only what is promised. I'm not sure what you mean by "misunderstandable" (which I don't believe is a word, btw). In fact, within R, because of S3 or S4 print/show methods there is no necessity at all that what is printed out on the screen has anything to do with what "typeof" will give.?print will give some details for S3 methods ?show for S4 methods,(provided the class package and associated Help files are loaded). So in that sense, there are an infinite number of "variables" (i.e. objects) where there is disagreement. In the sense that you ask (reading in a rectangular array?) please read ?data.frame and ?ead.table carefully. But it surely must depend on exactly how you are "importing" the data -- i.e., what R function you are using to do this. One thing to beware of: how missing data (blanks) in the Excel data or missing value codes like "NA" or "N/A" are handled. For example, read.table() will correctly interpret blanks in a text file given the correct number of field/delimiter specifications; but entries like "N/A" in a numeric field will be interpreted as characters, so that the numeric field will be converted to characters and then to factor unless you invoke the as.is=TRUE parameter (by which you can avoid your suggested ifelse construction, btw). Thus your typeof() invocation would give integer on what started off as a floating point column in Excel. So attention to detail and the software documentation is required! IMHO R's documentation is excellent, and truly remarkable given that it is an all volunteer effort. Please take advantage of it. -- Bert Gunter Genentech Non-Clinical Statistics South San Francisco, CA "The business of the statistician is to catalyze the scientific learning process." - George E. P. Box
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