Plotting heaviside (unit step) for circuits analysis not working (says "busy")?

Hi guys, I 'm trying to plot a simple heaviside function (unit step) for my summer circuits analysis course. When I click "RUN" on Matlab, it says BUSY on the bottom-left corner and just freezes. I have MATLAB R2017B installed with the symbolic math toolbox and I even just reinstalled it 2 minutes ago just to get a clean install.

This is my code:

clc
clear

t = -4:0.01:4;
f = 3 + (-2 - 3)*heaviside(t) + ((2*t-4) + 2).*heaviside(t-2);

plot(t,f);
xlabel('Time (s)')
ylabel('f(t)')
title('Plot of f(t) vs. t')
ylim([-3 4])

[Al Pizano]

Well I got it to work by updating MATLAB, however, does anyone know how to use the dirac delta to plot it? I have a unit step equation with a dirac delta of -2dirac(t-18) with t = -9:0.01:18; and I can't for the life of me get the dirac delta to plot!!!!