How to calculate the percentage of energy corresponding to the coefficients of one-dimensional wavelet decomposition ?

Hi, i read the matlab documentation about how to calculate the energy for 1-D wavelet decomposition and i found that it returns the percentage of energy corresponding to the approximations and details coefficients using this syntax :

[Ea,Ed] = wenergy(C,L)

I want to know how this calculation of percentage for each coefficients is done ? Actually i tried to calculate the energy with my own code using this code

 for i=1:1:1283
res=res+cd1(i)*cd1(i);
end
 x=res/1283;
D1=sqrt(x);

and i want to know how to calculate the percentage of energy of each coefficients used in this matlab syntax? Thanks