There are two things here.
1) Your function code is wrong at many places. You will have to rewrite it:
function D = BAT(P) % So D is the output and P is the input
D = 0; % D is initlalized as zero
DPold = [0.2;0.4;0.6;0.8]; % fine
Pold = [0;0;0;0]; % fine
if D < 0.2 % condition will pass
D = DPold(1); % D=0.2
Pold(1) = P; % Polt(1)=whatever value of P you are giving
elseif D < 0.4 & D >= 0.2 % i think you meant D < 0.4 && D >= 0.2; condition pass
D = DPold(2); % D=0.4
Pold(2) = P;% Polt(2)=whatever value of P you are giving
elseif D < 0.6 & D >= 0.4 % i think you meant D < 0.6 && D >= 0.4; condition pass
D = DPold(3);% D=0.6
Pold(3) = P;% Polt(3)=whatever value of P you are giving
elseif D < 0.8 & D >= 0.6 % i think you meant D < 0.8 && D >= 0.6; condition pass
D = DPold(4);% D=0.8
Pold(4) = P;% Polt(4)=whatever value of P you are giving
else % not required
end
% function end missing here
%% so basically your function outputs D=0.8
2) I wish to inject 4 duty cycles of 0.2, 0.4, 0.6, 0.8 one at a time: First of all correct your function as i explained above so that you get an array D=[0.2,0.4,0.6,0.8] as output. Then you can use bus to transmit all the values at once to the next block.
