The tcdf function calculates the student's t cumulative distribution function (CDF).

tcdf(x,degrees_of_freedom)

Student's t-CDF returns the probability that a single observation from the t distribution with ν degrees of freedom will fall in the interval [−∞, x):

Open

1. Create a 1-dimensional array of size 10 and fill it with values from 0.5 to 9.5:

   AFL% store(build(<x:double>[i=0:9], i+1/2.0), t_array);

2. Apply the tcdf function to the attribute x for four degrees of freedom:

   AFL% apply(t_array, t_cdf, tcdf(x, 4));

   
   The output is:

   {i} x,t_cdf {0} 0.5,0.678335 {1} 1.5,0.896 {2} 2.5,0.966617 {3} 3.5,0.987552 {4} 4.5,0.994589 {5} 5.5,0.997336 {6} 6.5,0.998555 {7} 7.5,0.999155 {8} 8.5,0.999475 {9} 9.5,0.999657

3. Remove the example array:

   AFL% remove(t_array);

itcdf: Inverse t-Student CDF