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Jan 30, 1993, 12:16:26 AM1/30/93

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Is there a factorial function in either the professional or

student edition of Matlab?? I have my student manual here and

I could not find a factorial function. If there is one, what

command do I use??

student edition of Matlab?? I have my student manual here and

I could not find a factorial function. If there is one, what

command do I use??

thanks

nabeel

P********************Palestinian Statehood Now!*****************************

E Nabeel Ibrahim | *

A ibr...@mentor.cc.purdue.edu | Oh, if humans could only *

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E Purdue University | *

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Jan 30, 1993, 10:25:09 AM1/30/93

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(Whew, at last an easy one.)

MATLAB does not have a factorial function, so n! must be computed by

prod(1:n)

or, possibly with roundoff error, by

gamma(n+1)

But, be careful, either of these quantities overflow for n > 170.

If you actually want n! to compute something like

n!/(k!*(n-k)!)

for large n, you should use

exp(sum(log(1:n))-sum(log(1:k))-sum(log(1:(n-k))))

It's not as slow as it looks, and it doesn't overflow.

-- Cleve Moler

Jan 31, 1993, 12:48:53 PM1/31/93

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mo...@MathWorks.COM (Cleve Moler) writes:

>MATLAB does not have a factorial function, so n! must be computed by

> prod(1:n)

>MATLAB does not have a factorial function, so n! must be computed by

> prod(1:n)

>If you actually want n! to compute something like

> n!/(k!*(n-k)!)

>for large n, you should use

> exp(sum(log(1:n))-sum(log(1:k))-sum(log(1:(n-k))))

I tried both of the above methods, but they don't seem to work

in loops. Specifically, I was trying to compute n!/(k!*(n-k)!)

for values of k from 0 to 10 while holding n at a constant

value of 10. Each time, n!/(k!*(n-k)!) was only computed

once. Any suggestions on how to fix this??

Thanks

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