R help - Sep 2013 - 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.

Hi,
You could try:
val1<- c(0.854400, 1.648465, 1.829830, 1.874704, 7.670915, 7.673585,
7.722619)
thresh1<- c(1,3,5,7,9)
rowSums(t(replicate(length(thresh1),val1))<= thresh1)
#[1] 1 4 4 4 7

#using ?sapply() could be shortened
sapply(thresh1,function(x) {sum(val1<x)})
#[1] 1 4 4 4 7


A.K.




----- Original Message -----
From: Zhang Weiwu <zhangweiwu at realss.com>
To: r-help at r-project.org
Cc: 
Sent: Friday, September 13, 2013 6:13 AM
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.

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

> 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.
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.