% operation for 441 nodes (11 mm BM length)
% 1.25:51, 1.75:71
% 2.25:91, 2.5:101, 2.75:111, 3.5:141, 3.75:151, 4.0:161, 4.25:171, 4.5:181
% 4.75:191

% the 'randinput' below is the inported random profile, either R1 or R2

dx = 0.025; % unit: mm
randinput_x = zeros(441,1);
xrange = 91:111;
randinput_x(xrange) = randinput;

x = (0:440)'*dx;

randinput_k = real(fft(randinput_x*dx));
k = 2*pi*linspace(0,1/dx,441);

figure
plot(k, abs(randinput_k),'-k','linewidth',0.5); 
set(gca,'FontSize',14);
xlabel('k (1/mm)','FontSize',14);
ylabel('Wavenumber Content','FontSize',14);