[R] how to get values within a threshold

[arun]

Hi Bill,

Great soluiton!
Just to add:
if values are not sorted (in this case, okay)

 set.seed(434)
  val1<- rnorm(1e5)
  set.seed(28)
  thresh1<- sample(1:20,1e2,replace=TRUE)
  system.time(res11<- findInterval(thresh1,val1))
#Error in findInterval(thresh1, val1) : 
 # 'vec' must be sorted non-decreasingly



system.time(res<- findInterval(thresh1,sort(val1)))
#   user  system elapsed 
 # 0.012   0.000   0.014 

system.time(res2<- sapply(thresh1,function(x) {sum(val1<x)}))
#   user  system elapsed 
 # 0.088   0.000   0.087 
 identical(res2,res)
#[1] TRUE



A.K.






----- Original Message -----
From: William Dunlap <wdunlap at tibco.com>
To: Zhang Weiwu <zhangweiwu at realss.com>; "r-help at r-project.org" <r-help at r-project.org>
Cc: 
Sent: Friday, September 13, 2013 10:44 AM
Subject: Re: [R] how to get values within a threshold

> findInterval(thresholds, values)
[1] 1 4 4 4 7

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Zhang Weiwu
> Sent: Friday, September 13, 2013 3:14 AM
> To: r-help at r-project.org
> Subject: [R] how to get values within a threshold
> 
> 
> input:
> 
>      > values
>      [1] 0.854400 1.648465 1.829830 1.874704 7.670915 7.673585 7.722619
> 
>      > thresholds
>      [1] 1 3 5 7 9
> 
> expected output:
> 
>      [1] 1 4 4 4 7
> 
> That is, need a vector of indexes of the maximum value below the threshold.
> 
> e.g.
> First  element is "1", because value[1] is the largest below threshold "1".
> Second element is "4", because value[4] is the largest below threshold "3".
> 
> The way I do it is:
> 
> > sapply(1:length(threshold), function(x) { length(values[values < threshold[x]])})
> [1] 1 4 4 4 7
> 
> It just seem to me too long and stupid to be like R. Is it already the best way?
> 
> Somehow I feel which() was designed for a purpose like this, but I couldn't
> figure out a way to apply which here.
> 
> ______________________________________________
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and provide commented, minimal, self-contained, reproducible code.