R help - Sep 2012 - help on setting boundaries for generating random numbers

Dear All,
 
is there a way to set low and high limits to a simulation with rlnorm()? 
 
as an example:
 a <-rlnorm(500,0.7,1)
 
 
I get the summary of
 
Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
 0.1175  1.0590  2.1270  3.4870  4.0260 45.3800   

I would like to set limits so that the simulated values minimum would be greater
then 0.5 and maximum of less than 30. If during simulation a value outside of
the limits would be simulated, then I would like R to "throw that value
out" and go back to generate another random number instead that would fit
the limits criteria.
 
Apreciate all the help on this,
 
Sincerely,
 
Andras
	[[alternative HTML version deleted]]

Hi,
May be this might help you.
set.seed(1)
?a <-rlnorm(500,0.7,1)
?a1<-a[a>30|a<0.5]
set.seed(2)
a2 <-rlnorm(500,0.7,1)
a3<-a2[a2>30|a2<0.5]
a4<-a2[!a2%in%a3]
summary(a4)
#?? Min. 1st Qu.? Median??? Mean 3rd Qu.??? Max. 
# 0.5105? 1.2500? 2.2990? 3.6850? 4.7140 25.3600 

a[a%in%a1]<-sample(a4,length(a[a%in%a1]),replace=FALSE)
summary(a)
#?? Min. 1st Qu.? Median??? Mean 3rd Qu.??? Max. 
# 0.5044? 1.2900? 2.1310? 3.5320? 4.1510 28.4800 
?a[a>30|a<0.5]
#numeric(0)
A.K.




----- Original Message -----
From: Andras Farkas <motyocska at yahoo.com>
To: "r-help at r-project.org" <r-help at r-project.org>
Cc: 
Sent: Saturday, September 1, 2012 5:29 AM
Subject: [R] help on setting boundaries for generating random numbers

Dear All,
?
is there a way to set low and high limits to a simulation with rlnorm()? 
?
as an example:
?a <-rlnorm(500,0.7,1)
?
?
I get the summary of
?
Min. 1st Qu.? Median? ? Mean 3rd Qu.? ? Max. 
 0.1175? 1.0590? 2.1270? 3.4870? 4.0260 45.3800? 

I would like to set limits so that the simulated values minimum would be greater
then 0.5 and maximum of less than 30. If during simulation a value?outside of
the limits would be simulated, then I would like R to "throw that value
out" and go back to generate another random number instead that would fit
the limits criteria.
?
Apreciate all the help on this,
?
Sincerely,
?
Andras
??? [[alternative HTML version deleted]]


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On Sat, Sep 01, 2012 at 02:29:40AM -0700, Andras Farkas
wrote:
> Dear All,
> ?
> is there a way to set low and high limits to a simulation with rlnorm()? 
> ?
> as an example:
> ?a <-rlnorm(500,0.7,1)
> ?
> ?
> I get the summary of
> ?
> Min. 1st Qu.  Median    Mean 3rd Qu.    Max. 
 0.1175  1.0590  2.1270  3.4870  4.0260 45.3800   
> 
> I would like to set limits so that the simulated values minimum would be
greater then 0.5 and maximum of less than 30. If during simulation a
value?outside of the limits would be simulated, then I would like R to
"throw that value out" and go back to generate another random number
instead that would fit the limits criteria.
Hi.

If you want to generate one number at a time, try this

  while (1) {
      a <- rlnorm(1, 0.7, 1)
      if (0.5 < a && a < 30) break
  }

If you want to generate a vector and avoid a loop over its components,
try something like the following

  n <- 500
  while (1) {
      a <- rlnorm(2*n, 0.7, 1)
      a <- a[0.5 < a & a < 30] # only one & here
      if (length(a) >= n) break
  }
  a <- a[1:n]

Hope this helps.

Petr Savicky.