function [pdf, centers] = isihist(isis, binwidth)
% Compute normalized histogram of interspike intervals.
%
% Arguments:
%   isis: vector of interspike intervals in seconds
%   binwidth: width in seconds to be used for the ISI bins
%
% Returns:
%   pdf: vector with pdf of interspike intervals in Hertz
%   centers: vector with centers of interspikeintervalls in seconds
    bins = 0.5*binwidth:binwidth:max(isis);
    % histogram data:
    [nelements, centers] = hist(isis, bins);
    % normalization (integral = 1):
    pdf = nelements / sum(nelements) / binwidth;
end