# [R] random numbers between 0 and 1

Rolf Turner r.turner at auckland.ac.nz
Wed Oct 21 21:46:25 CEST 2009

```On 22/10/2009, at 8:25 AM, carol white wrote:

> Hi,
> To generate random numbers between 0 and 1, do you use rnorm
> followed by dnrom? for ex, for 10 variables
>
> a = rnorm(10)
>> a
>  [1] -0.87640764 -0.95842391 -1.33434559 -0.63844932 -1.69829393
> 0.80010865
>  [7] -0.01026882 -0.23887516  2.29912600 -1.38352143
>> dnorm(a)
>  [1] 0.27171985 0.25202507 0.16378878 0.32538464 0.09432211 0.28966637
>  [7] 0.39892125 0.38772103 0.02838403 0.15320103

Well, this will give you random (in some sense) numbers between 0 and 1.
(Actually they will be between 0 and dnorm(0) = approx. 0.3989.)

Just what the *distribution* of these numbers would be is obscure to me.

You should also be aware that the values of dnorm() could be *larger*
than 1, if the standard deviation were specified to be something smaller
than the default value of 1.  (Note that dnorm() is a ***density***,
not a probability function.)

Anyway this is a very convoluted way of going at the problem.  Why
not just generate random numbers between 0 an 1 ``directly'', using
runif()?

cheers,

Rolf Turner

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