How to calculate the angular error

Dear Sir

      I am doing color constancy project it was define with angular error i got the formula but i don't now how to apply that if u gave any information about that it will help  to me please give any suggestion for that sir

                        Thanking you

[Steve Eddins]

What is the formula?

[Fathima Haleema]

The angular error ε is defined as the angular distance between the algorithm’s estimate of the light source (ee) and the true illuminant vector (el) in normalized

ε= Cos -1(el . ee ) this is the formula for calculation of angular error