How to catch integer 0

Question

Let s say we have a statement that produces integer 0   e g    a  lt - which 1 3    5    What is the safest way of catching this

User · Answer

if   length a  lt - which 1 3    5      print a   else print  nothing returned for  a       1   nothing returned for  a     On second thought I think any is more beautiful than length       if   any a  lt - which 1 3    5      print a   else print  nothing returned for  a      if   any a  lt - 1 3    5     print a   else print  nothing returned for  a

User · Answer

Maybe off-topic  but R features two nice  fast and empty-aware functions for reducing logical vectors -- any and all   if any x   dolphin    stop  Told you  no mammals

User · Answer

isEmpty   is included in the S4Vectors base package  No need to load any other packages  a  lt - which 1 3    5  isEmpty a     1  TRUE

User · Answer

Inspired by Andrie s answer  you could use identical and avoid any attribute problems by using the fact that it is the empty set of that class of object and combine it with an element of that class  attr a   quot foo quot    lt -  quot bar quot   identical 1L  c a  1L     gt   1  TRUE  Or more generally  is empty  lt - function x  mode   NULL       if  is null mode   mode  lt - class x      identical vector mode  1   c x  vector class x   1       b  lt - numeric 0   is empty a    gt   1  TRUE is empty a  quot numeric quot     gt   1  FALSE is empty b    gt   1  TRUE is empty b  quot integer quot     gt   1  FALSE

User · Answer

You can easily catch integer 0  with function identical x y  x   integer 0  identical x  integer 0    1  TRUE  foo   function x  identical x  integer 0    foo x   1  TRUE  foo 0   1  FALSE

User · Answer

If it s specifically zero length integers  then you want something like  is integer0  lt - function x      is integer x   amp  amp  length x     0L     Check it with   is integer0 integer 0    TRUE is integer0 0L           FALSE is integer0 numeric 0    FALSE     You can also use assertive for this   library assertive  x  lt - integer 0  assert is integer x  assert is empty x  x  lt - 0L assert is integer x  assert is empty x     Error  is empty   x has length 1  not 0  x  lt - numeric 0  assert is integer x  assert is empty x     Error  is integer   x is not of class  integer   it has class  numeric

User · Answer

another option is rlang  is empty  useful if you re working in the tidyverse  The rlang namespace does not seem to be attached when attaching the tidyverse via library tidyverse  - in this case you use purrr  is empty  which is just imported from the rlang package  By the way  rlang  is empty uses user Gavin s approach  rlang  is empty which 1 3    5     gt   1  TRUE

User · Answer

That is R s way of printing a zero length vector  an integer one   so you could test for a being of length 0   R gt  length a   1  0   It might be worth rethinking the strategy you are using to identify which elements you want  but without further specific details it is difficult to suggest an alternative strategy

[r] How to catch integer(0)?

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