primitive This function calculates the primitive of a given function supplied as input. y = primitive(f, t) y = primitive(f, t, x) f: t: This is an Octave function. This function calculates the primitive of a given function supplied as input. The second parameter t is a vector at which the output is evaluated (at the points t). This vector should be ascending and ordered. The function approximates the primitive (indefinite integral) of the univariate function handle f with constant of integration x.