What s the difference between integer class and numeric class in R

Question

I want to preface this by saying I m an absolute programming beginner  so please excuse how basic this question is    I m trying to get a better understanding of  atomic  classes in R and maybe this goes for classes in programming in general  I understand the difference between a character  logical  and complex data classes  but I m struggling to find the fundamental difference between a numeric class and an integer class    Let s say I have a simple vector x  lt - c 4  5  6  6  of integers  it would make sense for this to be an integer class  But when I do class x  I get  1   numeric   Then if I convert this vector to an integer class x  lt - as integer x   It return the same exact list of numbers except the class is different    My question is why is this the case  and why the default class for a set of integers is a numeric class  and what are the advantages and or disadvantages of having an integer set as numeric instead of integer

User · Accepted Answer

There are multiple classes that are grouped together as "numeric" classes, the 2 most common of which are double (for double precision floating point numbers) and integer. R will automatically convert between the numeric classes when needed, so for the most part it does not matter to the casual user whether the number 3 is currently stored as an integer or as a double. Most math is done using double precision, so that is often the default storage.

Sometimes you may want to specifically store a vector as integers if you know that they will never be converted to doubles (used as ID values or indexing) since integers require less storage space. But if they are going to be used in any math that will convert them to double, then it will probably be quickest to just store them as doubles to begin with.

User · Answer

First off  it is perfectly feasible to use R successfully for years and not need to know the answer to this question   R handles the differences between the  usual  numerics and integers for you in the background    gt  is numeric 1    1  TRUE   gt  is integer 1    1  FALSE   gt  is numeric 1L    1  TRUE   gt  is integer 1L    1  TRUE    Putting capital  L  after an integer forces it to be stored as an integer    As you can see  integer  is a subset of  numeric     gt   Machine integer max   1  2147483647   gt   Machine double xmax   1  1 797693e 308   Integers only go to a little more than 2 billion  while the other numerics can be much bigger   They can be bigger because they are stored as double precision floating point numbers   This means that the number is stored in two pieces  the exponent  like 308 above  except in base 2 rather than base 10   and the  significand    like 1 797693 above    Note that  is integer  is not a test of whether you have a whole number  but a test of how the data are stored   One thing to watch out for is that the colon operator     will return integers if the start and end points are whole numbers  For example  1 5 creates an integer vector of numbers from 1 to 5  You don t need to append the letter L    gt  class 1 5   1   integer    Reference  https   www quora com What-is-the-difference-between-numeric-and-integer-in-R

User · Answer

To quote the help page  try  integer   bolded portion mine   Integer vectors exist so that data can be passed to C or Fortran code which expects them  and so that  small  integer data can be represented exactly and compactly  Note that current implementations of R use 32-bit integers for integer vectors  so the range of representable integers is restricted to about   -2 10 9  doubles can hold much larger integers exactly   Like the help page says  R s integers are signed 32-bit numbers so can hold between -2147483648 and  2147483647 and take up 4 bytes  R s numeric is identical to an 64-bit double conforming to the IEEE 754 standard  R has no single precision data type   source  help pages of numeric and double   A double can store all integers between -2 53 and 2 53 exactly without losing precision  We can see the data type sizes  including the overhead of a vector  source    gt  object size 1 1000  4040 bytes  gt  object size as numeric 1 1000   8040 bytes

User · Answer

To my understanding - we do not declare a variable with a data type so by default R has set any number without L to be a numeric  If you wrote    gt  x  lt - c 4L  5L  6L  6L   gt  class x   gt  integer   it would be correct   Example of Integer     gt  x lt - 2L  gt  print x    Example of Numeric  kind of like double float from other programming languages    gt  x lt -3 4  gt  print x

[r] What's the difference between integer class and numeric class in R

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