# [R] Pseudo-random numbers between two numbers

(Ted Harding) Ted.Harding at manchester.ac.uk
Wed Mar 11 01:05:26 CET 2009

```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.
>> =================
>> 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.

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Date: 11-Mar-09                                       Time: 00:05:23
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