clear
load Belsk20
CIMEL=data;
load BelskPM25.mat

for k=1:length(CIMEL.doy)
 ind=find(CIMEL.year(k)==data.year&CIMEL.month(k)==data.month&CIMEL.day(k)==data.day&data.time>CIMEL.time(k)-0.5&data.time<CIMEL.time(k)+0.5);
 CIMEL.PM25(k)=mean(data.PM25(ind));
end