Assume your original table is called 'data', and results will be stored in a new table called 'new', then run:
new = table();
new.P_minus4 = [zeros(4,1);data.P(1:end-4)];
new.Q_minus4 = [zeros(4,1);data.Q(1:end-4)];
new.P_minus3 = [zeros(3,1);data.P(1:end-3)];
new.Q_minus3 = [zeros(3,1);data.Q(1:end-3)];
new.P_minus2 = [zeros(2,1);data.P(1:end-2)];
new.Q_minus2 = [zeros(2,1);data.Q(1:end-2)];
new.P_minus1 = [zeros(1,1);data.P(1:end-1)];
new.Q_minus1 = [zeros(1,1);data.Q(1:end-1)];
new.P = data.P;
new.Q = data.Q;
And you will get what you want. If you want the code to be more concise, run this lines:
new = table();
for i = 4:-1:1
m = num2str(i);
eval(['new.P_minus',m,' = [zeros(',m,',1);data.P(1:end-',m,')];']);
eval(['new.Q_minus',m,' = [zeros(',m,',1);data.Q(1:end-',m,')];']);
end
new.P = data.P;
new.Q = data.Q;
