MATLAB: “Reference to non-existent field” Error

MATLABmatlab guireference to non-existent field

I get this error (Reference to non-existent field 'system'.) when I use this line to call "generate_channel_cell" function 
H_cell= generate_channel_cell( system ) ;
The fuction code is as following: 
function channel_cell = generate_channel_cell(system)
p = inputParser ;
p.FunctionName = 'generate_channel_cell' ;
p.addRequired ('system') ;
Nt = round( p.Results.system.Nt ) ;
Nr = round( p.Results.system.Nr ) ;
Ns = round( p.Results.system.Ns ) ;
K = round( p.Results.system.K ) ;
coeff_size = [K * Nr , K * Nt ] ;   
coeffiecients = (randn(coeff_size ) + 1j .* randn( coeff_size ) ) ;
coeffiecients = (1 / sqrt ( 2 ) ) .* coeffiecients ;
Nr_values = repmat ([ Nr ] , 1 , K ) ;
Nt_values = repmat ([ Nt ] , 1 , K ) ;
channel_cell = mat2cell( coeffiecients , Nr_values , Nt_values ) ;
end % end function

Best Answer

Well, yes, you never use the input parser to parse your input, so the Results never get populated.
p.parse(system);
after you've created the parser but before you use the Results.
edit: on the other hand, your input parser is not very useful, it only checks that one input has been passed but you'll get an error beforehand if it's not the case. You don't check that the input is a structure with the correct fields
You'd be better off with:
function channel_cell = generate_channel_cell(system)
assert(isstruct(system) && all(ismember(fieldnames(system), {'Nt', 'Nr', 'Ns', 'K'}), 'system must be a structure with fields Nt, Nr, Ns and K');
Nt = round( p.Results.system.Nt ) ;
%...
Related Question