Undefined function 'cos' for input arguments of type 'char'. Error in solution (line 14)

What is wrong with line 14 of my script which is written as follows:

cos_AOI = cos(am(a))*cos(location_filename(:,2)) + sin(am(a))*sin(location_filename(:,2))

Gdirect = location_filename(:,4)*cos_AOI

Answer 1

[madhan ravi]

 str2double(location_filename(:,2))