Basic mathematical operations in R-console

Quotient:

syntex  divident/divisor=quotient
Ex. > 7/2
[1] 3.5

Integral quotient:
syntex   divident%/%divisor=integral quotient
Ex.
> 7%/%2
[1] 3 

Remainder:
syntex  divident%%divisor=remainder
Ex.
> 10%%3
[1] 1

Length of a string

syntex  length('var')

Ex.
> x=seq(1,9,0.5)
> x
 [1] 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0
> length(x)
[1] 17

Repeat n times a set of data
syntex  new _var=rep(existing_var, c(n)) 

Ex.
> y=rep(x,c(5))
> y
 [1] 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 1.0 1.5
[20] 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 1.0 1.5 2.0 2.5
[39] 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 1.0 1.5 2.0 2.5 3.0 3.5
[58] 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
[77] 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0
> length(y)
[1] 85