although i was more in to "simulik" with matlab i think that this is what u need

here is one m-file (that u need to make or u can write this directly in command window)

clear all

close all

clc

t=-5:0.01:5 ;

x=cos(10*pi*t)+sin(2*pi*t);

figure(1)

plot(t,x,'r')

axis([-5 5 -2.5 2.5])

title('x(t)=cos(10 \pi t )+sin (2 \pi t')

xlabel('t')

ylabel('x(t)')

grid on

or u can do in multicolor

like this

clear all

close all

clc

t=-5:0.01:5 ;

x1=exp((0.2+j*pi)*t);

x2=exp((-0.2+j*pi)*t);

x3=exp((0+j*pi)*t);

figure(2)

plot(t,real(x1))

hold on

plot(t,imag(x1),'r')

hold on

plot(t,real(x2),'--m')

hold on

plot(t,real(x3),'--k')

axis([-5 5 -2.5 2.5])

title('x(t)=e^{(\sigma+j\omega) t}')

xlabel('t')

ylabel('y(t)')

grid on

maybe you should post what is the function that you need to plot, or what values you need , maybe i'll remember something else that should be more acceptable to you and your supervisor

this you should get if u type that codes above ... easy you can change type and thickness of lines

Edit:

P.S. or if you don't know function that describe what you need, we can always (if u know in specific time intervals values of that function) approximate (very good) how doe's it act between two points... and lot's of another things