beta

Beta function.

SYNOPSIS:

double a, b, y, beta();
y = beta(a, b);

DESCRIPTION:
                -     -
               | (a) | (b)
beta(a, b) = -----------
                  -
                 | (a+b)

For large arguments the logarithm of the function is evaluated using lgam(), then exponentiated.

ACCURACY:
                      Relative error:
arithmetic   domain     # trials      peak         rms
    DEC        0,30        1700       7.7e-15     1.5e-15
    IEEE       0,30       30000       8.1e-14     1.1e-14

ERROR MESSAGES:

message           condition          value returned
overflow       log(beta) > MAXLOG         0.0
                a or b <0 integer          0.0