Error using plot Invalid data argument.

i am trying to plot x(t) = 2[u(t)-u(t-1)]

here are my steps including function y = U(t)

function y = U(t)
t = -3:0.0001:3;
y= 1*(t>=0);
plot(t,U(t))

xlabel ('t')

ylabel('y')

axis([-3 3 -1 2])
grid on

title('plot of the unit step function U(t)')

end

x(t) = 2[U(t)-U(t-1)]

x = @(t) 2*(U(t)-U(t-1))

plot(t,x(t))

[Alexandra McClernon Ownbey]

What is the error you are getting? Make sure you define subfunctions at the end of the script.

Answer 1

[Adam Danz]

function y = U(t) 
t = -3:0.0001:3;
y= 1*(t>=0);
plot(t,U(t))
%      ^^^^problem

You're recursively calling the U(t) function from within the function.

When sharing an error message, please share the entire copy-pasted message.

[Walter Roberson]

x(t) = 2[U(t)-U(t-1)]

Is invalid syntax in MATLAB. MATLAB does not have any implied multiplication at all, not even in the symbolic toolbox.

[Adam Danz]

That line is also invalid because t are floating point numbers rather than index values.

[Walter Roberson]

But U is a function, so it doesn't matter that t is not index values.