R object identification

Question

I am often ending up with a function producing output for which I don t understand the output data type  I m expecting a list and it ends up being a list of lists or a data frame or something else  What s a good method or workflow for figuring out the output data type when first using a function

User · Answer

str x    It s all you need to remember for 99  of cases

User · Answer

attributes someObject     Can also be useful

User · Answer

I usually start out with some combination of   typeof obj  class obj  sapply obj  class  sapply obj  attributes  attributes obj  names obj    as appropriate based on what s revealed   For example  try with   obj  lt - data frame a 1 26  b letters  obj  lt - list a 1 26  b letters  c list d 1 26  e letters   data cars  obj  lt - lm dist   speed  data cars      etc   If obj is an S3 or S4 object  you can also try methods or showMethods  showClass  etc   Patrick Burns  R Inferno has a pretty good section on this  sec  7    EDIT  Dirk and Hadley mention str obj  in their answers   It really is much better than any of the above for a quick and even detailed peek into an object

User · Answer

If I get  someObject   say via  someObject  lt - myMagicFunction        then I usually proceed by  class someObject  str someObject    which can be followed by head    summary    print        depending on the class you have

[r] R object identification

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