Here you go:

% Assume 't' is your time vector and 'y' is your signal

% 1. Shift the signal to start at zero

y_shifted = y - y(1);

% 2. Delete the first 4 seconds of the signal

trim_time = 4; % Time duration to trim

trim_index = find(t >= trim_time, 1); % Find the index corresponding to 4 seconds

t_trimmed = t(trim_index:end); % Trim the time vector

y_trimmed = y_shifted(trim_index:end); % Trim the signal

% 3. Ensure the signal starts at zero after trimming

y_final = y_trimmed - y_trimmed(1);

% Plotting the final signal

figure;

plot(t_trimmed, y_final);

xlabel('Time (s)');

ylabel('Signal Amplitude');

title('Signal After Trimming and Shifting');

% Step 1: Shift the entire signal to start at zero

shifted_signal = signal - signal(1);

% Step 2: Trim the first 4 seconds

trimmed_indices = t >= 4; % Logical index for time >= 4 seconds

trimmed_signal = shifted_signal(trimmed_indices);

trimmed_time = t(trimmed_indices);

% Step 3: Ensure the trimmed signal starts at zero

final_signal = trimmed_signal - trimmed_signal(1);

% Plot the result to visualize

figure;

plot(trimmed_time, final_signal);

xlabel('Time (s)');

ylabel('Amplitude');

title('Processed Signal');

grid on;

You can follow these steps:

% Assume 't' is the time vector and 'signal' is the signal data

% 1. Shift the signal to start at zero

signal_shifted = signal - signal(1);

% 2. Delete the first 4 seconds of the signal

% Assume 'Fs' is the sampling frequency

t_new = t(t >= 4);

signal_trimmed = signal_shifted(t >= 4);

% 3. Ensure the signal starts at zero after trimming

signal_final = signal_trimmed - signal_trimmed(1);

% Plot the final signal

plot(t_new, signal_final);

xlabel('Time (s)');

ylabel('Amplitude');

title('Processed Signal');

To shift and trim a signal in MATLAB:

These operations adjust the position and length of the signal for analysis or processing.