function rasterplot(spikes, tmax)
% Display a spike raster of the spike times given in spikes.
%
% rasterplot(spikes, tmax)
%   spikes: a cell array of vectors of spike times in seconds
%   tmax: plot spike raster upto tmax seconds

    ntrials = length(spikes);
    for k = 1:ntrials
        times = spikes{k};
        times = times(times<tmax);
        if tmax < 1.5
            times = 1000.0*times; % conversion to ms
        end
        for i = 1:length( times )
            line([times(i) times(i)],[k-0.4 k+0.4], 'Color', 'k'); 
        end
    end
    if tmax < 1.5
        xlabel('Time [ms]');
        xlim([0.0 1000.0*tmax]);
    else
        xlabel('Time [s]');
        xlim([0.0 tmax]);
    end
    ylabel('Trials');
    ylim([0.3 ntrials+0.7]);
end