The R Book

Modulo and Integer Quotients

Integer quotients and remainders are obtained using the notation %/% (percent, divide, percent) and %% (percent, percent) respectively. Suppose we want to know the integer part of a division: say, how many 13s are there in 119:

119 %/% 13

[1]  9

Now suppose we wanted to know the remainder (what is left over when 119 is divided by 13): in maths this is known as modulo:

119 %% 13

[1]  2

Modulo is very useful for testing whether numbers are odd or even: odd numbers have modulo 2 value 1 and even numbers have modulo 2 value 0:

9 % % 2

[1]  1

8%%   2

[1]     0

Likewise, you use modulo to test if one number is an exact multiple of some other number. For instance to find out whether 15 421 is a multiple of 7, ask:

15421 % % 7 == 0

[1]  TRUE