Question

Here is my problem:

myvec <- c(1, 2, 2, 2, 3, 3,3, 4, 4, 5, 6, 6, 6, 6, 7, 8, 8, 9, 10, 10, 10)

I want to develop a function that can caterize this vector depending upon number of categories I define.

if categories 1 all newvec elements will be 1

if categories are 2 then

unique (myvec), i.e.

1 = 1, 2 =2, 3 = 1, 4 = 2, 5 =1, 6 = 2, 7 = 1, 8 = 2, 9 = 1, 10 = 2

(which is situation of odd or even numbers)

If categories are 3 then first three number will be 1:3 and then pattern will be repeated.

1 = 1, 2 = 2, 3=3, 4=1, 5 = 2, 6 = 3, 7 =1, 8 = 2, 9 = 3, 10 =1 

If caterogies are 4 then first number will be 1:4 and then pattern will be repeated

1 = 1, 2 = 2, 3= 3, 4 = 4, 5 = 1, 6 = 2, 7=3, 8=4, 9 =1, 10 = 2

Similarly for n categories the first 1:n, then the pattern repeated.

Answer 1

Using the recycling features of R (this gives a warning if the vector length is not divisible by n):

R> myvec <- c(1, 2, 2, 2, 3, 3, 3, 4, 4, 5, 6, 6, 6, 6, 7, 8, 8, 9, 10, 10, 10)
R> n <- 3
R> y <- cbind(x=sort(unique(myvec)), y=1:n)[, 2]
R> y
 [1] 1 2 3 1 2 3 1 2 3 1

or using rep:

R> x <- sort(unique(myvec))
R> y <- rep(1:n, length.out=length(x))
R> y
 [1] 1 2 3 1 2 3 1 2 3 1

Update: you could just use the modulo operator

R> myvec
 [1]  1  2  2  2  3  3  3  4  4  5  6  6  6  6  7  8  8  9 10 10 10
R> n <- 4
R> ((myvec - 1) %% n) + 1
 [1] 1 2 2 2 3 3 3 4 4 1 2 2 2 2 3 4 4 1 2 2 2