Plotting FRF with imaginary and real numbers

% Example FRF data (complex numbers)
FRF_data = [
    -0.0915237963199616 + 0.00000000000000i;
    -0.0666214004158974 - 0.0629538968205452i;
    -0.0647708997130394 - 0.0962110981345177i;
    0.000384484999813139 - 0.189506992697716i;
    0.104717001318932 - 0.171706005930901i;
    0.145686000585556 - 0.117163002490997i;
    0.148408994078636 - 0.0817890018224716i;
    0.150115996599197 - 0.0637563988566399i;
    0.149434000253677 - 0.0457847006618977i;
    0.151601999998093 - 0.0343611985445023i;
    0.144703000783920 - 0.0156481992453337i;
    0.134606003761292 - 0.00748514989390969i;
    0.119563996791840 - 0.00314980000257492i
];

% Frequency vector (assume evenly spaced if not provided)
num_points = length(FRF_data);
frequencies = linspace(0, 100, num_points); % Example frequency range (0 to 100 Hz)

% Compute magnitude and phase
magnitude = abs(FRF_data); % Compute magnitude
phase = angle(FRF_data);   % Compute phase (in radians)

% Plot the results
figure;
subplot(2, 1, 1);
plot(frequencies, magnitude, 'b-', 'LineWidth', 1.5);
title('FRF Magnitude');
xlabel('Frequency (Hz)');
ylabel('Magnitude');
grid on;

subplot(2, 1, 2);
plot(frequencies, phase, 'r-', 'LineWidth', 1.5);
title('FRF Phase');
xlabel('Frequency (Hz)');
ylabel('Phase (radians)');
grid on;

Notes:

1. Frequency Vector:

   • If you have the corresponding frequency values for each data point, use them.
   • If not, assume evenly spaced frequency values.

2. Additional Plots:

   • You can also plot the real and imaginary parts separately if needed:

real_part = real(FRF_data);
imag_part = imag(FRF_data);
plot(frequencies, real_part, 'g', frequencies, imag_part, 'm');
legend('Real Part', 'Imaginary Part');

1. Interpretation:

   • Peaks in the magnitude plot often correspond to natural frequencies.
   • Phase changes provide insight into the system's behavior near these frequencies.