Hi,
Some speed comparison
set.seed(434)
val1<- rnorm(1e5)
set.seed(28)
thresh1<- sample(1:20,1e2,replace=TRUE)
system.time(res<- rowSums(t(replicate(length(thresh1),val1))<= thresh1))
# user system elapsed
# 0.320 0.064 0.382
system.time(res2<- sapply(thresh1,function(x) {sum(val1<x)}))
# user system elapsed
# 0.088 0.004 0.093
system.time(res3<-
rowSums(matrix(rep(val1,length(thresh1)),nrow=length(thresh1),byrow=TRUE)<=thresh1))
# user system elapsed
# 0.228 0.048 0.275
system.time(res4<-
sapply(1:length(thresh1),function(x){length(val1[val1<thresh1[x]])}))
# user system elapsed
# 0.300 0.044 0.345
mat1<- matrix(rep(val1,length(thresh1)),nrow=length(thresh1),byrow=TRUE)
system.time(res5<- rowSums(mat1<=thresh1))
# user system elapsed
# 0.104 0.000 0.103
system.time(res6<- unlist(lapply(thresh1,function(x) {sum(val1<x)})))
# user system elapsed
# 0.088 0.000 0.088
identical(res,as.numeric(res2))
#[1] TRUE
identical(res,res3)
#[1] TRUE
identical(res,as.numeric(res4))
#[1] TRUE
identical(res,as.numeric(res6))
#[1] TRUE
A.K.
----- Original Message -----
From: arun <smartpink...@yahoo.com>
To: Zhang Weiwu <zhangwe...@realss.com>
Cc: R help <r-help@r-project.org>
Sent: Friday, September 13, 2013 9:27 AM
Subject: Re: [R] how to get values within a threshold
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 <zhangwe...@realss.com>
To: r-help@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.
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______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
