rmeddis@0: function VS=UTIL_vectorStrength(PH)
rmeddis@0: % UTIL_vectorStrength converts a period histogram to a vector strength measure.
rmeddis@0: % **************
rmeddis@0: % using the Johnson(1980) formula.
rmeddis@0: % usage:
rmeddis@0: % 	VS=UTIL_vectorStrength(PH);
rmeddis@0: %
rmeddis@0: % Input arguments:
rmeddis@0: % 	PH is channels x  period histogram matrix
rmeddis@0: %
rmeddis@0: % Output argumkents:
rmeddis@0: % VS is a column of vector strengths, one per channel
rmeddis@0: [numChannels K]=size(PH);
rmeddis@0: 
rmeddis@0: % a=cos(2*pi*(1/K:1/K:1));
rmeddis@0: % b=sin(2*pi*(1/K:1/K:1));
rmeddis@0: % VS=(sum(PH.*repmat(a,numChannels,1),2).^2 + sum(PH.*repmat(b,numChannels,1),2).^2).^0.5;
rmeddis@0: % warning off MATLAB:divideByZero
rmeddis@0: % VS=VS./sum(PH,2);
rmeddis@0: % warning on MATLAB:divideByZeroa=cos(2*pi*(1/K:1/K:1));
rmeddis@0: 
rmeddis@0: 
rmeddis@0: a=cos(2*pi*(1/K:1/K:1));
rmeddis@0: b=sin(2*pi*(1/K:1/K:1));
rmeddis@0: N=sum(PH,2);
rmeddis@0: warning off MATLAB:divideByZero
rmeddis@0: VS=((sum(PH.*repmat(a,numChannels,1),2)./N).^2 ...
rmeddis@0:     + (sum(PH.*repmat(b,numChannels,1),2)./N).^2).^0.5;
rmeddis@0: warning on MATLAB:divideByZero