I have a bug on my code

It keeps saying u(t) is not defined even though I did.

% t bounded between -1 and 1 with a step of 0.01 
t = -1:0.01:1;
%Plot on a graph 
x_1 = 5 * u(t-0.1);
x_2 = 2 * rectangularPulse(t/0.3);
x_3 = 4 * sinc(t/0.2);
figure
plot(t,x1,'g',t,x2fx,'b',t,x3,'c');

Unrecognized function or variable 'x1'.

% Label the graph 
xlabel('Amplitude')
ylabel('Time t[s]')
title('Assignment 3')
legend("x1(t)","x2(t)","x3(t)");
grid on;
% Step function implementing 𝑦(𝑡) = 𝑢(𝑡)
function y =u(t)
y(t > 0) = 1;
y(t == 0) = 0.5;
y(t < 0) = 0;
end

% Rectangular pulse function implementing 𝑦(𝑡) = Π(𝑡)
function y = rectangularPulse(t)
y = (t >= -0.5 & t <= 0.5);
end
% Sinc function implementing 𝑦(𝑡) = 𝑠𝑖𝑛𝑐(𝑡)
function y = sinc(t)
y = (sin(pi.*t) / pi.*t);
end

[Stephen23]

You have not defined the following variables/functions: x1, x2fx, x3.

Once you define those variables then your code works:

% t bounded between -1 and 1 with a step of 0.01 
t = -1:0.01:1;
%Plot on a graph 
x1 = 5 * u(t-0.1);                % fixed name
x2 = 2 * rectangularPulse(t/0.3); % fixed name
x3 = 4 * sinc(t/0.2);             % fixed name
figure
plot(t,x1,'g',t,x2,'b',t,x3,'c');
% Label the graph 
xlabel('Amplitude')
ylabel('Time t[s]')
title('Assignment 3')
legend("x1(t)","x2(t)","x3(t)");
grid on;

% Step function implementing 𝑦(𝑡) = 𝑢(𝑡)
function y = u(t)
y(t > 0) = 1;
y(t == 0) = 0.5;
y(t < 0) = 0;
end

% Rectangular pulse function implementing 𝑦(𝑡) = Π(𝑡)
function y = rectangularPulse(t)
y = (t >= -0.5 & t <= 0.5);
end

% Sinc function implementing 𝑦(𝑡) = 𝑠𝑖𝑛𝑐(𝑡)
function y = sinc(t)
y = (sin(pi.*t) / pi.*t);
end

Answer 1

[Image Analyst]

You have not defined x1. x1 is a differently-named variable than x_1.

1. If they should be the same variable, then use a consistent name, either with or without the underline.
2. Otherwise if they are different variables you need to define exactly what x1 is.