so this would be the code :
samples = 1000;
input_signal = 1 + sin(2*pi*(1:samples)/samples)+ 0.025*rand(1,samples);
decim_factor = 20; % nb of samples / decimation
output_signal = zeros(1,samples); % pre allocation
% zero overlap mean averaging
for ci=1:floor(samples/ decim_factor)
start_index = 1+(ci-1)*decim_factor;
stop_index = min(start_index+ decim_factor,length(input_signal));
output_signal(start_index:stop_index) = input_signal(start_index);
end
figure(1),
plot((1:samples),input_signal,'b',(1:samples),output_signal,'-r');
