find value from matriks

i have matriks A with size (64,4), so the variables is part of A = [A1 A2 A3 A4] i want to process them, to find a value ei=A3-(0.5*A1) and fi = A4-(0.5*A2). so the output is 64 value of ei and 64 value of fi.

Answer 1

[the cyclist]

ei = A(:,3) - 0.5*A(:,1);
fi = A(:,4) - 0.5*A(:,2);

Answer 2

[Thorsten]

 A = rand(64, 4);

 ei = A(:,3) - 0.5*A(:, 1);
 fi = A(:,4) - 0.5*A(:, 2);