Data Analysis with R, Second Edition - Second Edition

Arithmetic and assignment

Check out the following example:

  > 2 + 2 
  [1] 4 
 
  > 9 / 3 
  [1] 3 
 
  > 5 %% 2    # modulus operator (remainder of 5 divided by 2) 
  [1] 1 

Anything that occurs after the octothorpe or pound sign, #, (or hash-tag for you young'uns), is ignored by the R interpreter. This is useful to document the code in natural language. These are called comments.

In a multi-operation arithmetic expression, R will follow the standard order of operations from math. In order to override this natural order, you have to use parentheses flanking the sub-expression that you'd like to be performed first:

   > 3 + 2 - 10 ^ 2        # ^ is the exponent operator 
   [1] -95 
   > 3 + (2 - 10) ^ 2 
   [1] 67 

In practice, almost all compound expressions are split up with intermediate ...