[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:
>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
>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)

     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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