incorrect number or types of inputs or outputs for function 'int'

When I put this code with int function, it always says in red: Wrong type or number in function int. Tried to change units, tried all which I could do.

Any advices?

% Define the parameters of the signal
A = 1;            % Amplitude
T_0 = 4*pi;       % Period
t = linspace(0, T_0, 1000); % Time vector

% Generate the signal
y = A*cos(4*pi*t/T_0);

% Calculate the power of the signal using integration
power = (1/T_0) * int((y).^2, t(1), t(end));

Incorrect number or types of inputs or outputs for function 'int'.

% Plot the signal
plot(t, y);
xlabel("Time (s)");
ylabel("Amplitude");
title("A*cos(4*pi*t/T_0)");

% Display the signal power
disp(['Signal power = ' num2str(power)]);

Answer 1

[Torsten]

% Define the parameters of the signal
A = 1;            % Amplitude
T_0 = 4*pi;       % Period
syms t
% Generate the signal
y = A*cos(4*pi*t/T_0);
% Calculate the power of the signal using integration
power = (1/T_0) * int(y^2)

power = 

power = matlabFunction(power)

power = function_handle with value:
    @(t)t.*3.978873577297384e-2+sin(t.*2.0).*1.989436788648692e-2

y = matlabFunction(y)

y = function_handle with value:
    @(t)cos(t)

t_num = linspace(0, T_0, 1000); % Time vector
y_num = y(t_num);
% Plot the signal
plot(t_num, y_num);
xlabel("Time (s)");
ylabel("Amplitude");
title("A*cos(4*pi*t/T_0)");

% Display the signal power
power_num = power(t_num(end))-power(t_num(1));
disp(['Signal power = ' num2str(power_num)]);

Signal power = 0.5

Answer 2

[Alan Stevens]

Replace your power calculation with

power = (1/T_0) * trapz(t,y.^2);

Edited - Walter is correct.

[Walter Roberson]

power = (1/T_0) * trapz(t, y.^2);

seems more likely

[Gary]

Thank you very much for your answer, I also got the same result using sum function. However, suppose if there is only function 'int()' that can integrate other functions rather than trapz, integral, sum, et cetera... How should I make the code?

[Steven Lord]

The int function to perform integration is only defined for symbolic inputs, not numeric inputs. So this works:

syms x
int(x^2)

ans = 

but this doesn't.

y = (1:10).^2;
int(y)

Incorrect number or types of inputs or outputs for function 'int'.

In your code y is a vector of values not a symbolic expression.

[Gary]

Thank you for your grateful, thoughtful words!!