Incomplete beta function
I = betainc(X,Z,W)
I = betainc(X,Z,W,tail)
The incomplete beta function is
where , the beta function, is defined as
and is the gamma function.
I = betainc(X,Z,W) computes the incomplete beta function for corresponding elements of the arrays X, Z, and W. The elements of X must be in the closed interval [0,1]. The arrays Z and W must be nonnegative and real. All arrays must be the same size, or any of them can be scalar.
'lower' (the default)
Computes the integral from 0 to x
Computes the integral from x to 1
These functions are related as follows:
1-betainc(X,Z,W) = betainc(X,Z,W,'upper')
Note that especially when the upper tail value is close to 0, it is more accurate to use the 'upper' option than to subtract the 'lower' value from 1.
format long betainc(.5,(0:10)',3) ans = 1.00000000000000 0.87500000000000 0.68750000000000 0.50000000000000 0.34375000000000 0.22656250000000 0.14453125000000 0.08984375000000 0.05468750000000 0.03271484375000 0.01928710937500