load battery;

for i=year(1):year(end);
    ii=i-year(1)+1;
    k=find(year==i);
    h=H(k);
    j=find(isfinite(h));
    if(length(j)>=4000);
    eta(ii)=mean(h(j));
else
    eta(ii)=NaN;
end
    YR(ii)=i;
end
subplot(2,1,1);
plot(YR,eta);
hold on
plot(YR,eta,'.');
i=find(YR>=1925&YR<=1965);
j=find(isfinite(eta(i)));
P1=polyfit(YR(i(j)),eta(i(j)),1);
HH=polyval(P1,YR(i(j)));
plot(YR(i(j)),HH,'k');


i=find(YR>=1965);
j=find(isfinite(eta(i)));
P2=polyfit(YR(i(j)),eta(i(j)),1);
HH=polyval(P2,YR(i(j)));
plot(YR(i(j)),HH,'k');