# How to do MATLAB plotting in time for my examples?

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#### james the cat

##### Newbie level 3 Can anyone please tell me what I need to do to enable me make MAPLAB plot the following outputs against time

i.e.

1. Here I am differentiating the system step response, to show that this give the impulse response, but how do I make MATLAB do “plot(t,x)” where t is 0 to 8ms and x is the step response differentiated.

clear
num=[0 0 2021004.003];
den=[1 1421.73674 1010502.002];
t=(0:0.00001:8e-3);
y=step(num,den,t);
x=diff ;
x=x*100000;
plot(x)
xlabel(‘Time ( 10e-6 seconds)’), ylabel(‘Amplitude’),
title(‘System Step Response Differentiated’)
axis([0 800 –200 1000])

2. Here I am convolving the sin wave input y with the system impulse response, to find the system output, but how do I make MATLAB do “plot(t,z)” and “plot(t,z,t,y) i.e the system input and output together where t is 0 to 1s, y is the sine wave input and z is y convolved with the systems impulse response.

clear
num=[0 0 2021004.003];
den=[1 1421.73674 1010502.002];
t=(0:0.0001:1);
x=impulse(num,den,t);
y=((4/pi)*(sin(2*pi*30*t)));
z=conv(y,x);
plot(z)

I know that this can be done using the lsim command but am wanting to know how to do it as shown above.

Any one any ideas

Regards James

S

#### socboy

##### Guest in your second case, i donno if u could plot the o/p vs time. you are dealing with disceret system where time info is lost.

you can plot the input and output on same plot using these

plot(input);
hold on
plot(output);

hope this helps ...

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