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+%======================================================================
+%                    V E C _ C O H E R E N C E . M 
+%                    doc: Wed Aug  8 09:01:59 2012
+%                    dlm: Wed Aug  8 10:19:53 2012
+%                    (c) 2012 A.M. Thurnherr
+%                    uE-Info: 58 27 NIL 0 0 72 10 2 4 NIL ofnI
+%======================================================================
+
+% calculate coherence between two 2-D vector time-series or profiles
+%	- time or space is coded in 1st vector dimension
+%	- code based on [ladcp_cohere.m] by X. Liang
+%	- XL had hard-coded nsegs=4
+
+function coh = vec_coherence(v1,v2,nsegs,conf)
+
+valid = find(isfinite(v1(:,2)));
+v1 = v1(find(isfinite(v1(:,2))),:);
+v2 = v2(find(isfinite(v2(:,2))),:);
+
+rez1 = median(diff(v1(:,1)));
+rez2 = median(diff(v2(:,1)));
+
+if (rez1 ~= rez2)
+	error('incompatible vector resolutions');
+end
+
+first = max(min(v1(:,1)),min(v2(:,1)));
+last  = min(max(v1(:,1)),max(v2(:,1)));
+
+cv1 = v1(find(v1(:,1)>=first&v1(:,1)<=last),2) + sqrt(-1)*v1(find(v1(:,1)>=first&v1(:,1)<=last),3);
+cv2 = v2(find(v2(:,1)>=first&v2(:,1)<=last),2) + sqrt(-1)*v2(find(v2(:,1)>=first&v2(:,1)<=last),3);
+
+if (length(cv1) ~= length(cv2))
+	error('incompatible vectors');
+end
+    
+NFFT = floor(length(cv1)/nsegs) ;						% segment data
+freq = -1/(2*rez1):1/((NFFT-1)*rez1):1/(2*rez1);		% spectral frequencies
+coh.conf = conf;
+coh.clim = sqrt(1-(1-conf)^(1/(nsegs-1)));				% Confidence limit (Data analysis methods in physical oceanography, p488)
+
+s1 = fftshift(fft(cv1,NFFT));							% power spectra
+s2 = fftshift(fft(cv2,NFFT));
+
+s12 = conj(s1).*s2;  %Inner-cross spectrum				% cross spectra
+s21 = fliplr(s1).*s2; %outer-cross spectrum
+s11 = abs(s1).^2;
+s22 = abs(s2).^2;
+    
+for i = 1:NFFT/nsegs									% frequency-average spectra
+	as12(i) = mean(s12((i-1)*nsegs+1:i*nsegs));
+	as21(i) = mean(s21((i-1)*nsegs+1:i*nsegs));
+	as11(i) = mean(s11((i-1)*nsegs+1:i*nsegs));
+	as22(i) = mean(s22((i-1)*nsegs+1:i*nsegs));
+	coh.freq(i) = mean(freq((i-1)*nsegs+1:i*nsegs));
+end
+    
+coh.period = 1 ./ coh.freq;
+coh.mag   = sqrt(abs(as12).^2./(as11.*as22));
+coh.phase = atan2(-imag(as12),real(as12))*(180/pi);
+    
+figure
+subplot(211)
+plot(coh.freq,coh.mag)
+hold on
+line([coh.freq(1) coh.freq(end)],[coh.clim coh.clim],'color','r')
+xlim([coh.freq(1) coh.freq(end)])
+xlabel('Frequency/Wavenumber [cycles/unit]')
+ylabel('Inner Rotary Coherence')
+grid on
+text(coh.freq(fix(0.8*length(coh.freq))), coh.clim+0.05, sprintf('%d%%',100*coh.conf));
+    
+subplot(212)
+plot(coh.freq,coh.phase)
+xlim([coh.freq(1) coh.freq(end)])
+ylim([-180 180])
+xlabel('Frequency/Wavenumber [cycles/unit]')
+ylabel('Phase angle [deg]')
+grid on
+