function [y,t] = euler(z, yz, y0, t0, dt, steps)
ys = [y0];
ts = [t0];
for i=2:steps
    ts(i) = ts(i-1)+dt;
    if yz-ys(i-1)>0
      ys(i) = ys(i-1)+dt*((yz*3)-3*ys(i-1))+z;
    else
      ys(i) = ys(i-1)+dt*(5-3*ys(i-1))-z;
    end
end
y = ys;
t = ts;
endfunction

[y,t] = euler(0.2,13,0,0,0.1, 100);
plot(t,y);