Excellent, thank you, exactly what I was looking for.
On Dec 9, 2:07 pm, "William Stein" <[EMAIL PROTECTED]> wrote:
> On Tue, Dec 9, 2008 at 2:04 PM, Jason Bandlow <[EMAIL PROTECTED]> wrote:
>
> > Hi Matthew,
>
> > Matthew J wrote:
> >> Sage is great software that I rave about in pretty much all of my
> >> classes except for probability theory. I'd like to get some info on a
> >> few topics to clear some things up so that I can use these for classes
> >> and to post to an examples worksheet. Thanks in advance to anyone that
> >> replies.
>
> >> I am wondering how to do a few things.
> >> Is there a better (built-in) way to do simple combinations/
> >> permutations than writing a function like
>
> >> def choose(n,k): return factorial(n)/(factorial(k)*factorial((n-k)))
>
> > Entering: binomial(5,2)
> > will return: 10
>
> > Is this what you want? (This is much more efficient than the 'choose'
> > function you have above.)
> >> or equivalent for permutations?
>
> > I'm not sure exactly what you mean here. factorial(n) counts the number
> > of permutations of 'n' elements very efficiently. Perhaps you mean
>
> > sage: permutations([1,2,2])
> > [[1, 2, 2], [2, 1, 2], [2, 2, 1]]
>
> > Type permutations? for more information on this command. You may also
> > be interested in the command 'combinations'.
>
> >> -----
>
> >> Is there a way to get the Standard Normal CDF other than writing the
> >> function explicitly like below?
>
> >> def normalCDF(z):
> >> t = var('t')
> >> return N(integrate((1/sqrt(2*pi))*e^((-t^2)/2), t, -infinity, z))
> >> -----
>
> >> Also, are there any distributions built into sage? I don't quite know
> >> what working with a distribution symbolically would be like, but as an
> >> example, perhaps being able to do something like
> >> X ~ BIN(n, p) and then get the expected value, variance, or PDF of X?
> >> Assume that n and p are given.
>
> > *Lots* of statistics is built into sage with the 'R' package. I don't
> > know it well, but you can try typing R? inside sage and see what you can
> > work out from there.
>
> Sage also includes the scipy.stats package, which has 100 or
> so distributions:
>
> sage: import scipy.stats
> sage: help(scipy.stats)
>
> William
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