How do I plot a trapezoidal function?

x=linspace(-4,8,500);
y=(square((x*(3/2)+3)));
t=(sawtooth((x*(3/2)+3)));
v=[-4 8 0 2];
s=(3/2)/2;
for n=1:3
a=-(2)/(n^(2)*pi^2);
b=-(1)/(n*pi);
s=s+a*cos((n*pi*x)/2)+b*sin((n*pi*x)/2);
figure(1),subplot(2,2,n),plot(x,y,x,s,x,t),axis(v)
end

The above is what I have so far, and it looks sort of how I want it to look, except I want it to not have a line because of the use a mix of sawtooth and square waves to make it look like a proper trapezoidal wave. Also it should be periodic T+4 as opposed to 2pi periodic as sawtooth and square functions have as standard.

Any help is greatly appreciated.