Pseudo-random numbers between two numbers
Because of a mistake I made in copying code into email, there has been confusion (expressed in some private emails). Hence the corrected version is appended at the end.
On 11-Mar-09 00:05:26, Ted Harding wrote:
I have modified my example to make it more convincing! See at end. On 10-Mar-09 23:39:17, Ted Harding wrote:
On 10-Mar-09 23:01:45, guox at ucalgary.ca wrote:
Please forget the last email I sent with the same subject.
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I would like to generate pseudo-random numbers between two numbers
using R, up to a given distribution, for instance, norm. That is
something like
rnorm(HowMany,Min,Max,mean,sd)
over rnorm(HowMany,mean,sd).
I am wondering if
qnorm(runif(HowMany, pnorm(Min,mean,sd), pnorm(Max,mean, sd)),
mean, sd)
is good. Any idea? Thanks.
-james
It would certainly work as intended! For instance:
truncnorm<-function(HowMany,Min,Max,mean=0,sd=1){
qnorm(runif(HowMany, pnorm(Min,mean,sd), pnorm(Max,mean, sd)),
mean, sd)}
Sample <- truncnorm(1000,-1,2.5)
hist(Sample,breaks=100)
Hoping this helps,
Ted.
truncnorm<-function(HowMany,Min,Max,mean=0,sd=1){
qnorm(runif(HowMany, pnorm(Min,mean,sd), pnorm(Max,mean, sd)),
mean, sd)}
Sample <- truncnorm(100000,-1,2.5)
hist(Sample,breaks=100)
u0<-(-0.975)+0.05*(0:69)
yy<-dnorm(u0)
du<-min(diff(H$breaks))
Y <- 100000*yy*du/(pnorm(2.5)-pnorm(-1.0))
lines(u0,Y)
Ted.
Corrected version:
------------------
truncnorm<-function(HowMany,Min,Max,mean=0,sd=1){
qnorm(runif(HowMany, pnorm(Min,mean,sd), pnorm(Max,mean, sd)),
mean, sd)}
Sample <- truncnorm(100000,-1,2.5)
H <- hist(Sample,breaks=100)
u0<-(-0.975)+0.05*(0:69)
yy<-dnorm(u0)
du<-min(diff(H$breaks))
Y <- 100000*yy*du/(pnorm(2.5)-pnorm(-1.0))
lines(u0,Y)
Apologies for the error.
Ted.
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E-Mail: (Ted Harding) <Ted.Harding at manchester.ac.uk>
Fax-to-email: +44 (0)870 094 0861
Date: 11-Mar-09 Time: 19:48:12
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