The function apply_nn.m is a MATLAB function that approximates the scattering properties of raindrops. This function is specifically designed to simulate the scattering properties of raindrops at W-band frequencies and a 30° elevation angle.

The file nn_coefficients.mat must be located in the same folder as the apply_nn.m function.

You can call the function from the MATLAB command line as follows:

y = apply_nn(x)

where x represents the drop diameter, which must be in the range of 0.1 to 4.5 mm. 
The output y contains the scattering properties for one drop per cubic meter:

y(1,:) is reflectivity [dBZ]
y(2,:) is differential reflectivity Zdr [dB] 
y(3,:) is backscattering phase Delta [°]
y(4,:) is attenuation [dB km^-1] 
y(5,:) is differential attenuation [dB km^-1]
y(6,:) is specific phase shift [° km^-1]