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101_software/fwhm.m

+function width = fwhm(x,y)
+
+% function width = fwhm(x,y)
+%
+% Full-Width at Half-Maximum (FWHM) of the waveform y(x)
+% and its polarity.
+% The FWHM result in 'width' will be in units of 'x'
+%
+%
+% Rev 1.2, April 2006 (Patrick Egan)
+
+
+y = y / max(y);
+N = length(y);
+lev50 = 0.5;
+if y(1) < lev50                  % find index of center (max or min) of pulse
+    [garbage,centerindex]=max(y);
+    Pol = +1;
+%     disp('Pulse Polarity = Positive')
+else
+    [garbage,centerindex]=min(y);
+    Pol = -1;
+%     disp('Pulse Polarity = Negative')
+end
+i = 2;
+while sign(y(i)-lev50) == sign(y(i-1)-lev50)
+    i = i+1;
+end                                   %first crossing is between v(i-1) & v(i)
+interp = (lev50-y(i-1)) / (y(i)-y(i-1));
+tlead = x(i-1) + interp*(x(i)-x(i-1));
+i = centerindex+1;                    %start search for next crossing at center
+while ((sign(y(i)-lev50) == sign(y(i-1)-lev50)) & (i <= N-1))
+    i = i+1;
+end
+if i ~= N
+    Ptype = 1;  
+%     disp('Pulse is Impulse or Rectangular with 2 edges')
+    interp = (lev50-y(i-1)) / (y(i)-y(i-1));
+    ttrail = x(i-1) + interp*(x(i)-x(i-1));
+    width = ttrail - tlead;
+else
+    Ptype = 2; 
+%     disp('Step-Like Pulse, no second edge')
+    ttrail = NaN;
+    width = NaN;
+end