function y=f(t)
y = zeros(size(t)); % Preallocating enough memory for y
tmod=mod(t,4)-2;
region1 = (tmod<0) & (tmod>=-2); % First interval
y(region1) = -tmod(region1).^2;
region2 = (tmod>=0) & (tmod<=2); % Second interval
y(region2) = tmod(region2).^2;
Now you can do this:
t = -10:0.1:10;
y = f(t);
plot(t, y)
Best wishes
Torsten.
