# how can I calculate movmean from 1 periode wave data?

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christina widyaningtyas on 14 Jun 2022
Answered: Peter Perkins on 14 Jun 2022
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

Mathieu NOE on 14 Jun 2022
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');

Peter Perkins on 14 Jun 2022

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