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gamma

gamma — The gamma function.

Calling sequence

 y = gamma(x)

Parameters

x : real vector or matrix
y : real vector or matrix with same size than x.

Description

gamma(x) evaluates the gamma function at all the elements of x. The gamma function is defined by :



                     /+oo
                     |   x-1  -t
         gamma(x) =  |  t    e    dt
                     /0

and generalizes the factorial function for real numbers (gamma(n+1) = n!).

Examples



// simple examples
gamma(0.5)
gamma(6)-prod(1:5)

// the graph of the Gamma function on [a,b]
a = -3; b = 5;
x = linspace(a,b,40000)';
y = gamma(x);
xbasc()
c=xget("color")
xset("color",2)
plot2d(x, y, style=0, axesflag=5, rect=[a, -10, b, 10])
xset("color",c)
fs=xget("font")
xset("font",4,2)
xtitle("The gamma function on ["+string(a)+","+string(b)+"]")
xset("font",fs(1),fs(2))
xselect()

See also

gammaln, dlgamma

Author

W. J. Cody and L. Stoltz (code from Netlib (specfun))

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