[R] how to write a periodic function in R?

Duncan Murdoch murdoch at stats.uwo.ca
Mon Jul 25 17:43:07 CEST 2005

On 7/25/2005 11:22 AM, lma5 at ncsu.edu wrote:
> My question is how to write a periodic function in R.
> for example if there is a function f(x) that
>  f(x)=f(x+4), for -2<x<2, f(x)=x
> how to write it in R?
> thanks a lot!

Just write a function that does that, e.g.

f <- function(x) (x + 2) %% 4 - 2

The %% is the mod operator, so (x + 2) %% 4 adds 2 then maps all values 
into the range 0 to 4.  You'll need a different formula for a different 
periodic function.

Use plot(f, from=-7, to=7) to see that this works.

Duncan Murdoch

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