how can I calculate movmean from 1 periode wave data?

I have data :

x-axis is datetime - experiment time start (called as t=0)

y-axis is pressure

How to calculate the moving average of one periode wave data (example like this figure)?

X is time 00:21:00 to 00:22:58

Y is pressure 931 to 931

I use 2016b and sometimes 2020 Matlab version

I hope someone can help me, please

thank you

Answer 1

[Mathieu NOE]

hello

we can use the peaks to compute this value as well

you can use islocalmax (or islocalmin) to locate local peaks.

Some smoothing may help if yur data are a bit noisy or "hairy"

see demo below

clc
clearvars

% demo on dummy data
n=1000;
x = linspace(0,10,n)';
y = 931*(0.9+0.1*cos(x/10))+10*sin(3*x-1)+ 5*rand(n,1);

% some smoothing first
ys = smoothdata(y,'gaussian',25);

% find positive local maxima
[tf, P] = islocalmax(ys,'MinProminence',std(ys)/3);
x_peak = x(tf);
y_peak = ys(tf);

% compute average of pressure on cycle by cycle
for ci = 1:numel(x_peak)-1
    ind = (x>=x_peak(ci) & x<x_peak(ci+1));
    y_avg(ci) = mean(y(ind));
    x_avg(ci) = (x_peak(ci) + x_peak(ci+1))/2; % time value (plot) = mid point between two x_peak values
end

figure(1)
plot(x,y,'b',x,ys,'g',x_peak,y_peak,'dr',x_avg,y_avg,'+-k','linewidth',2,'markersize',12);
xlabel('time')
ylabel('pressure')
legend('raw signal','filtered signal','peaks','averaged cycle value');

Answer 2

[Peter Perkins]

In addition to what Mathieu suggests, there are similar things shown in these examples, especially the first one:

https://www.mathworks.com/help/matlab/matlab_prog/find-events-in-timestamped-data.html

https://www.mathworks.com/help/matlab/matlab_prog/add-events-from-external-data-to-timetable.html