cycle to cyle period of a signal--matlab

input:

time series of displacement

 

output

 

code

% key function: findpeaks
clear;
clc;
%% read data
%data=xlsread('nogapur5.xlsx');
data=importdata('data.txt');
t=data(1:2000,1); % time, 3s
dis=data(1:2000,2); % dis
dis_nor=dis./0.1; % dis nor
lift=data(1:2000,3); % lift
drag=data(1:2000,4); % drag
%%%%%%%%%%%%%%%%%%%% fig. 1 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
figure(1);
plot(t,dis_nor,'k-');
xlabel('\it t(s)','fontsize',10,'fontname','Times New Roman');
ylabel('\it Dis./fn','fontsize',10,'fontname','Times New Roman');
[pks,locs]=findpeaks(dis,t); % peaks and locations
% plot the peaks using findpeaks and label them
findpeaks(dis,t);
text(locs+.02,pks,num2str((1:numel(pks))'));
saveas(gcf,'peaks','jpg');
T=diff(locs);
f=1./T;
fn=1.46;
f_nor=f./fn;
time=locs(2:end);
%%%%%%%%%%%%%%%%%%%% fig. 2 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
figure(2);
plot(time,f_nor,'k:o');
xlabel('\it t(s)','fontsize',10,'fontname','Times New Roman');
ylabel('\it f_{osc}/fn','fontsize',10,'fontname','Times New Roman');
%% figure size
% fig = gcf ;
% fig.PaperUnits = 'inches';
% fig.PaperPosition = [0 0 4 3];
saveas(gcf,'f_osc_vs_time','jpg');