[R] function of probability for normal distribution

David Winsemius dwinsemius at comcast.net
Thu Jan 20 04:41:02 CET 2011

On Jan 19, 2011, at 6:03 PM, JClark wrote:

> Dear Greg Snow,
> I'm a biologist trying to write a mathematical formula for a doubly
> truncated normal distribution to be used in the language "R". I  
> realise this
> is simple stuff for a mathematician but I'm stumped.
> Wikipedia gives what seems a fairly simple formula - with function =  
> maths
> with mean and standard deviation - but also phi - WHAT IS PHI !!?? -

Capital phi is the cdf of the Normal distribution and lowercase phi is  
the density (the cdf's derivative). You can see fairly standard usage  
in the Definition and Cumulative distribution function sections of the  
Wikipedia page.

> especially how do I write this in "R"

You will need these:


> and why is the top "phi" in italics ??

You are being unreasonably vague here. You are apparently looking at  
<something>. We are looking at a plaintext message.  Perhaps you are  
(mis)calling a lowercase phi as italic?

Maybe you should read the Posting Guide and the items it links to  
regarding how to ask a good question??



David Winsemius, MD
West Hartford, CT

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