attributes.m

来自「这是matlab在地球物理数据处理方面的源码」· M 代码 · 共 44 行

function [envelope,instphi,instfreq] = attributes(traces,t)
% function attributes - calculates the amplitude envelope, the instantaneous phase,
% and the instantaneous frequency for a set of seismic traces
% The program uses the Matlab Hilbert transform function.
% The envelope is simply the absolute value of the output of the Hilbert transform.
% That is, the real part is the input function and the imaginary part is its Hilbert
% transform. The Hilbert transform produces the 90 degree phase shifted version of
% the input trace.
% The instantaneous phase is simply the angle(unwrap(hilbert(traces))) and the
% instantaneous phase is the derivative of this function with respect to time.
% The instantaneous frequency is not really a frequency but has the same units of
% frequency.

delt  = t(2) - t(1);
[m,n] = size(traces);

temp = hilbert(traces);  % Note that traces must be in column format

instphi = unwrap(angle(temp));
envelope = abs(temp);

temp = diff(instphi)/delt;  fil = [0.2 0.2 0.2 0.2 0.2]; % For smoothing
for i = 1:n
   instfreq(:,i) = conv(fil,temp(:,i)); % Smoothed derivative
end
figure
subplot(1,2,1)
imagesc(1:n,t,traces);
title('original traces')
ylabel('time (seconds)')
subplot(1,2,2)
imagesc(1:n,t,envelope)
title('Amplitude Envelope')
colorbar
figure
subplot(1,2,1)
imagesc(1:n,t,instphi)
title('Instantanteous Phase')
subplot(1,2,2)
imagesc(1:n,t,instfreq)
colorbar

return;