function [tp, f, index] = freq(t,x)
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Function to calculate firing frequency
%
% inputs: t - time vector
% x - oscillating function (indices should match t)
%
% outputs: tp - time points
% f - corresponding frequency (at that time point)
% index - indices of the time vector
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
k=1;
index=1;
tp=t(1);
for i=1:length(t)-1
if (x(i)<-0&x(i+1)>-0),
tp(k)=t(i);
k=k+1;
index = i;
end
end
try
f=[1./diff(tp)];
f=[f, f(end)];
tp=[tp];
catch
tp=[t(1) t(end)];
f=[0, 0];
end
end