Error Bars and Interpretation
- From: "LindsE" <LindsEHillier@xxxxxxxxx>
- Date: 21 Mar 2007 07:12:39 -0700
Good day, everyone;
I'm plotting a best fit line to a timeseries of temperature data from
1885 to 1995, in an attempt to identify whether there has be a
significant change in temperature in the particular region. I am
attempting to determine whether the slope is significant at the 95%
level by plotting confidence limits. I am also trying to provide
statistical evidence, using error bars, as requested, to determine
whether there has been a significant change in temperature over this
time frame.
1) Can anyone tell me how to determine if the slope is significant?
2) I have error bars plotted, but they seem to increase as time goes
on. I can't seem to think why this might happen. Any suggestions?
3) How can I determine if the temperature change has been significant
using these bars?
I used the following commands:
figure(1)
subplot(3,1,1);hold on
[pH1,sH] = polyfit(xx,HUseF,1);
[yH1,delta] = polyval(pH1,xx,sH);
plot(xx,HUseF,'.g','MarkerSize',5)
plot(xx,yH1,'k','LineWidth',2)
plot(xx,yH1+2*delta,'-.r','MarkerSize',1)
plot(xx,yH1-2*delta,'-.r','MarkerSize',1)
L=yH1+2*std(yH1);
errorbar(xx(1:50:end),yH1(1:50:end),L(1:50:end),'k')
ylabel('Temperature ({\circ}C)')
xlabel('Year')
set(gca,'XTick',x3(1:120:end))
set(gca,'XTickLabel',
{'1885','1895','1905','1915','1925','1935','1945','1955','1965','1975','1985','1995'})
title('Linear Fit to Deseasoned, Smoothed Time Series')
Sorry for the non-technical question, but I'm out of practise in the
statistics department.
Thanks;
Lindsay
grid on
.
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