[R] breaks

[Sundar Dorai-Raj]

Erin Hodgess wrote:
> Dear R People:
> 
> I have a question about a "sorting" problem, please.
> 
> I have a vector xx:
> 
> 
>>xx
> 
> 
>  [1] -2.0  1.4 -1.2 -2.2  0.4  1.5 -2.2  0.2 -0.4 -0.9
> 
> and a vector of breaks:
> 
> 
>>xx.y
> 
> 
> [1] -2.2000000 -0.9666667  0.2666667  1.5000000
> 
> I want to produce another vector z which contains the number of the class
> that each data point is in.
> 
> for instance, xx[1] is between xx.y[1] and xx.y[2], so z[1] == 1
> 
> this can be accomplished via loops, but I was wondering if there is a more
> efficient method, please.
> 
> By the way, eventually, there will be many more data points and more
> classes.
> 

I think what you're looking for is ?cut:

R> xx = c(-2.0,  1.4, -1.2, -2.2,  0.4,  1.5, -2.2,  0.2, -0.4, -0.9)
R> cut(xx, breaks = c(-Inf, -2.2, -0.97, 0.27, 1.5, Inf))
  [1] (-2.2,-0.97] (0.27,1.5]   (-2.2,-0.97] (-Inf,-2.2]  (0.27,1.5]
  [6] (0.27,1.5]   (-Inf,-2.2]  (-0.97,0.27] (-0.97,0.27] (-0.97,0.27]
Levels: (-Inf,-2.2] (-2.2,-0.97] (-0.97,0.27] (0.27,1.5] (1.5,Inf]
R>

Regards,
Sundar