Check if the number is integer

Question

I was surprised to learn that R doesn t come with a handy function to check if the number is integer   is integer 66    FALSE   The help files warns      is integer x  does not test if x   contains integer numbers  For that    use round  as in the function   is wholenumber x  in the examples    The example has this custom function as a  workaround   is wholenumber  lt - function x  tol    Machine double eps 0 5   abs x - round x    lt  tol is wholenumber 1    is TRUE   If I would have to write a function to check for integers  assuming I hadn t read the above comments  I would write a function that would go something along the lines of  check integer  lt - function x        x    round x      Where would my approach fail  What would be your work around if you were in my hypothetical shoes

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In R  whether a number is numeric or integer can be determined by class function  Generally all numbers are stored as numeric and to explicitly define a number as integer we need to specify  L  after the number  Example   x  lt - 1 class x    1   quot numeric quot   x  lt - 1L class x    1   quot integer quot  I hope this is what was needed  Thanks

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Reading the R language documentation  as integer has more to do with how the number is stored than if it is practically equivalent to an integer  is integer tests if the number is declared as an integer   You can declare an integer by putting a L after it    gt  is integer 66L   1  TRUE  gt  is integer 66   1  FALSE   Also functions like round will return a declared integer  which is what you are doing with x  round x    The problem with this approach is what you consider to be practically an integer   The example uses less precision for testing equivalence    gt  is wholenumber 1 2 -50   1  TRUE  gt  check integer 1 2 -50   1  FALSE   So depending on your application you could get into trouble that way

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It appears that you do not see the need to incorporate some error tolerance  It would not be needed if all integers came entered as integers  however sometimes they come as a result of arithmetic operations that loose some precision  For example    gt  2 49 49  1  2  gt  check integer 2 49 49   1  FALSE   gt  is wholenumber 2 49 49   1  TRUE   Note that this is not R s weakness  all computer software have some limits of precision

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Once can also use dplyr  near   library dplyr   near a  as integer a     It applies to any vector a  and has an optional tolerance parameter

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From Hmisc  spss get   all floor x     x  na rm   TRUE    much safer option  IMHO  since it  bypasses  the machine precision issue  If you try is integer floor 1    you ll get FALSE  BTW  your integer will not be saved as integer if it s bigger than  Machine integer max value  which is  by default 2147483647  so either change the integer max value  or do the alternative checks

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you can use simple if condition like   if round var     var

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Here is one  apparently reliable way   check integer  lt - function N        grepl      digit      format N   digits   20  scientific   FALSE      check integer 3243   TRUE check integer 3243 34   FALSE check integer  sdfds    FALSE   This solution also allows for integers in scientific notation    gt  check integer 222e3   1  TRUE

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I am not sure what you are trying to accomplish  But here are some thoughts   1  Convert to integer   num   as integer 123 2342    2  Check if a variable is an integer    is integer num  typeof num    integer

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UPDATE                                                                  Respect to the  OLD  answer here below  I have discovered that it worked because I have put all the numbers in a single atomic vector  one of them was a character  so every one become characters   If we use a list  hence  coercion does not happen  all the test pass correctly but one  1  1 - 0 98   which remains a numeric  This because the tol parameter is by default 100    Machine double eps and that number is far from 50 little less than the double of that  So  basically  for this kind of numbers  we have to decide our tolerance   So if you want all test became TRUE  you can assertive  is whole number x  tol   200    Machine double eps   Anyway  I confirm that IMO assertive remains the best solution   Here below a reprex for this  UPDATE      expect trues c  lt - c    cl   sqrt 2  2    pp   9 0    t   1    1 - 0 98     ar0   66L    ar1   66    ar2   1   2 -50    v   222e3    w1   1e4    w2   1e5    v2    1000000000000000000000000000000000001     an   2   49   49    ju1   1e22    ju2   1e24    al   floor 1     v5   1 0000000000000001   this is under machine precision     str expect trues c    gt   Named chr  1 15   2   9   50   66   66   1   222000   10000   1e 05        gt   - attr     names    chr  1 15   cl   pp   t   ar0      assertive  is whole number expect trues c    gt  Warning  Coercing expect trues c to class  numeric     gt                       2                      9                     50    gt                    TRUE                   TRUE                   TRUE    gt                      66                     66                      1    gt                    TRUE                   TRUE                   TRUE    gt                  222000                  10000                 100000    gt                    TRUE                   TRUE                   TRUE    gt                   1e 36                      2                  1e 22    gt                    TRUE                   TRUE                   TRUE    gt  9 9999999999999998e 23                      1                      1    gt                    TRUE                   TRUE                   TRUE    expect trues l  lt - list    cl   sqrt 2  2    pp   9 0    t   1    1 - 0 98     ar0   66L    ar1   66    ar2   1   2 -50    v   222e3    w1   1e4    w2   1e5    v2    1000000000000000000000000000000000001     an   2   49   49    ju1   1e22    ju2   1e24    al   floor 1     v5   1 0000000000000001   this is under machine precision     str expect trues l    gt  List of 15   gt     cl   num 2   gt     pp   num 9   gt     t    num 50   gt     ar0  int 66   gt     ar1  num 66   gt     ar2  num 1   gt     v    num 222000   gt     w1   num 10000   gt     w2   num 1e 05   gt     v2   chr  1000000000000000000000000000000000001    gt     an   num 2   gt     ju1  num 1e 22   gt     ju2  num 1e 24   gt     al   num 1   gt     v5   num 1 assertive  is whole number expect trues l    gt  Warning  Coercing expect trues l to class  numeric     gt  There was 1 failure    gt    Position              Value      Cause   gt  1        3 49 999999999999957 fractional assertive  is whole number expect trues l  tol   200    Machine double eps    gt  Warning  Coercing expect trues l to class  numeric     gt      2 0000000000000004                      9     49 999999999999957    gt                    TRUE                   TRUE                   TRUE    gt                      66                     66     1 0000000000000009    gt                    TRUE                   TRUE                   TRUE    gt                  222000                  10000                 100000    gt                    TRUE                   TRUE                   TRUE    gt                   1e 36     1 9999999999999998                  1e 22    gt                    TRUE                   TRUE                   TRUE    gt  9 9999999999999998e 23                      1                      1    gt                    TRUE                   TRUE                   TRUE    expect falses  lt - list    bb   5 - 1e-8    pt1   1 0000001    pt2   1 00000001    v3   3243 34    v4    sdfds     str expect falses    gt  List of 5   gt     bb   num 5   gt     pt1  num 1   gt     pt2  num 1   gt     v3   num 3243   gt     v4   chr  sdfds  assertive  is whole number expect falses    gt  Warning  Coercing expect falses to class  numeric     gt  Warning in as this class x   NAs introduced by coercion   gt  There were 5 failures    gt    Position              Value      Cause   gt  1        1 4 9999999900000001 fractional   gt  2        2 1 0000001000000001 fractional   gt  3        3 1 0000000099999999 fractional   gt  4        4 3243 3400000000001 fractional   gt  5        5                lt NA gt     missing assertive  is whole number expect falses  tol   200    Machine double eps    gt  Warning  Coercing expect falses to class  numeric      gt  Warning  NAs introduced by coercion   gt  There were 5 failures    gt    Position              Value      Cause   gt  1        1 4 9999999900000001 fractional   gt  2        2 1 0000001000000001 fractional   gt  3        3 1 0000000099999999 fractional   gt  4        4 3243 3400000000001 fractional   gt  5        5                lt NA gt     missing   Created on 2019-07-23 by the reprex package  v0 3 0    OLD                                                                     IMO the best solution comes from the assertive package  which  for the moment  solve all positive and negative examples in this thread      are all whole numbers  lt - function x      all assertive  is whole number x   na rm   TRUE     are all whole numbers c    cl   sqrt 2  2    pp   9 0    t   1    1 - 0 98     ar0   66L    ar1   66    ar2   1   2 -50    v   222e3    w1   1e4    w2   1e5    v2    1000000000000000000000000000000000001     an   2   49   49    ju1   1e22    ju2   1e24    al   floor 1     v5   1 0000000000000001   difference is under machine precision       gt  Warning  Coercing x to class  numeric     gt   1  TRUE  are all not whole numbers  lt - function x      all  assertive  is whole number x   na rm   TRUE     are all not whole numbers c    bb   5 - 1e-8    pt1   1 0000001    pt2   1 00000001    v3   3243 34    v4    sdfds       gt  Warning  Coercing x to class  numeric     gt  Warning in as this class x   NAs introduced by coercion   gt   1  TRUE   Created on 2019-07-23 by the reprex package  v0 3 0

User · Answer

For a vector m  m round m     m  will return the indices of values in the vector that are not integers

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Another alternative is to check the fractional part   x  1  0   or  if you want to check within a certain tolerance   min abs c x  1  x  1-1     lt  tol

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Here s a solution using simpler functions and no hacks    all equal a  as integer a     What s more  you can test a whole vector at once  if you wish   Here s a function   testInteger  lt - function x     test  lt - all equal x  as integer x   check attributes   FALSE    if test    TRUE   return TRUE      else   return FALSE        You can change it to use  apply in the case of vectors  matrices  etc

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If you prefer not to write your own function  try check integer from package installr  Currently it uses VitoshKa s answer    Also try check numeric v  only integer TRUE  from package varhandle  which has the benefit of being vectorized

[r] Check if the number is integer

Examples related to r

Examples related to integer

Examples related to rounding