R help - Jun 2014 - Interval for rnorm command?

Hello everyone!

I want to create a data vector using the "rnorm" command. Let's
say /x <-
rnorm(100, 1, 2)/. This gives me 100 values from the specific normal
distribution. However, I want to generate a variable that has a certain
range of values, e.g. values can't exceed the interval /[-3.7; 3.7]/. How
can I implement such an interval? 

Thanks for your help and sorry if this is totally trivial, I am new to R. 



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On 08/06/14 02:23, zagreus wrote:
> Hello everyone!
>
> I want to create a data vector using the "rnorm" command.
Let's say /x <-
> rnorm(100, 1, 2)/. This gives me 100 values from the specific normal
> distribution. However, I want to generate a variable that has a certain
> range of values, e.g. values can't exceed the interval /[-3.7; 3.7]/.
How
> can I implement such an interval?
What you are asking for amounts to drawing a sample from a *truncated* 
normal distribution.

Try

	RSiteSearch("truncated normal")

to find appropriate functions to effect this procedure.

cheers,

Rolf Turner

Hi,

You may try:
fun1 <- function(len, low, high, mean, sd) {
??? x <- rnorm(len * 2, mean, sd)
??? x <- x[x < high & x > low]
??? x[1:len]
}

##slow
fun2 <- function(len, low, high, mean, sd) {
??? i <- 1
??? while (i < len) {
??????? x <- rnorm(1, mean, sd)
??????? if (x < high & x > low) {
??????????? i <- i + 1
??????? }
??? }
??? x
}


set.seed(42)
?res1 <- fun1(100,-3.7, 3.7, 1,2)
?set.seed(42)
?res2 <- fun1(100,-3.7, 3.7, 1,2)


identical(res1,res2)
#[1] TRUE
range(res1)
#[1] -2.562617? 3.640227
A.K.












On Saturday, June 7, 2014 10:28 PM, zagreus <a0906257 at
unet.univie.ac.at> wrote:
Hello everyone!

I want to create a data vector using the "rnorm" command. Let's
say /x <-
rnorm(100, 1, 2)/. This gives me 100 values from the specific normal
distribution. However, I want to generate a variable that has a certain
range of values, e.g. values can't exceed the interval /[-3.7; 3.7]/. How
can I implement such an interval? 

Thanks for your help and sorry if this is totally trivial, I am new to R. 



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http://r.789695.n4.nabble.com/Interval-for-rnorm-command-tp4691856.html
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