[R] Creating a specific skewed distribution

[Greg Snow]

Your question is somewhat vague, there are probably an infinite number of distributions that fit your description.

Here are 2 possibilities:

> tmp <- sample( c(1,30,60), 10000000, replace=TRUE, 
+ prob=c(0.10344, 0.9-0.10344, 0.1))
> mean(tmp)
[1] 30.00041
> mean(tmp>=60)
[1] 0.1001004
> 
> tmp2 <- rgamma(10000000, shape=1.777666, scale=30/1.777666)
> mean(tmp2)
[1] 29.99674
> mean(tmp2>=60)
[1] 0.0999903

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of David Arnold
> Sent: Tuesday, June 09, 2009 11:49 PM
> To: r-help at r-project.org
> Subject: [R] Creating a specific skewed distribution
> 
> All,
> Can someone help me create a skewed distribution, mean = 30, with
> probability of selecting a random number from the distribution greater
> than or equal 60 equal to 10%?
> 
> I need the probability density function to equal zero at zero, and
> have  a maximum height at or near 30.
> 
> Is this possible?
> 
> And if it is possible, how can I adjust the distribution so that the
> probability of selecting a random number greater than or equal to 60
> is p.
> 
> Thanks. No idea how to start.
> 
> David
> 
> 
> 
> 	[[alternative HTML version deleted]]
> 
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