emd.rar_EMD 台湾_EMD由台湾黄_MATLAB emd包

Tutorial for the HHT MATLAB program

A few examples of how to use these programs are given, with a given dataset “gsta.dat”,

which is the annual mean global surface temperature anomaly. In “gsta.dat”, the first column is the

time; and the second is the corresponding data value.

1) Load and display data

>> load gsta.dat;

>> plot(gsta(:,1),gsta(:,2));

>> axis([1850 2010 -0.6 0.6]);

>> title('the annual mean global surface temperature anomaly')

>> year=gsta(:,1);

>> inData=gsta(:,2);

>> rslt=eemd(inData,0,1);

>> plot(year,rslt(:,2));

>> hold on;

>> plot(year,rslt(:,3)-0.3);

>> plot(year,rslt(:,4)-0.6);

>> plot(year,rslt(:,5)-0.9);

>> plot(year,sum(rslt(:,6:8),2)-1.3,'r-');

>> hold off

It should be noted that since in the eemd.m, the total number of IMFs m is specified as

log2(N)-1, in some occasions (such as the one in this example), the components may be

excessively extracted. In these cases, the sum of the latest columns may already satisfy

the definition of a trend.

3) Instantaneous frequency of an IMF

The instantaneous frequency can be obtained through calling ifndq.m function:

>> axis([1850 2010 -0.12 0.12]);

>> title('IMF C3');

>> ylabel('Kelvin');

>> grid;

>> subplot(2,1,2);

>> plot(year, omega_m3/2/pi,'r-');

>> grid;

>> xlabel('year');

>> ylabel('cycle/year');

>> title('instantaneous frequency');