[R] Random Numbers
Bernardo Rangel Tura
tura at centroin.com.br
Sat Aug 17 13:11:00 CEST 2002
At 15:48 17/08/2002 +1200, you wrote:
>hi,
>
>Actually this applies not just to random numbers, but...
>
>Suppose I type:
> x <- rnorm(30, 4, 1.5)
>to get some 30 random normal numbers with mean 4 and standard deviation
>1.5.
>
>Is there anyway to "re-trace" x? i.e. am I able to find out what the mean
>and standard deviation for x is?
>
>More generally, suppose I generated some random numbers using a particular
>distribution. Can I find out the parameters of the distribution on these
>random numbers?
Well use fitdistr ()
require (mass)
x <- rnorm(30, 4, 1.5)
fitdistr(x,"normal",list(mean=0,sd=1))
result:
mean sd
3.7126893 1.2748764
(0.2327595) (0.1646173)
Warning message:
NaNs produced in: dnorm(x, mean, sd, log)
Thanks in advance
Bernardo Rangel Tura, MD, MSc
National Institute of Cardiology Laranjeiras
Rio de Janeiro Brazil
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