function data = optostim_compare(date_string, locations_index, first_trace_index, number_cycles, ...
    traces_plot, locations_plot)
if nargin == 0
    disp('usage: optostim_compare(''14-Apr-2005'', 7, 8, 4, [2 2 1 1], [3 3 2 2])');
    disp('this will read locations from 007, 4 cycles of traces starting from 008');
    disp('will plot traces in figure 2 suplot (2,1,1) and mark locations in figure 3 subplot (3,2,2)');
    return
end
locations_index_string = sprintf('%03d', locations_index);
locations_file = [date_string '_' locations_index_string '_locations.dat'];
locations = load(locations_file)
locations_x = zeros(1,0);
locations_y = zeros(1,0);
total_locations = size(locations,1);
for index = 1:total_locations
    locations_x = [locations_x locations(index,1)];
    locations_y = [locations_y locations(index,2)];
end
locations_x = repmat(locations_x,2,1);
locations_y = repmat(locations_y,2,1);
if nargin > 5
    figure(locations_plot(1));
    subplot(locations_plot(2),locations_plot(3),locations_plot(4));
    hold on
    set(gca, 'DefaultLineMarkerSize',12)
    plot(locations_x, locations_y, '*');
end
if nargin > 4
    figure(traces_plot(1));
    subplot(traces_plot(2),traces_plot(3),traces_plot(4));
end
empty = 1;
for cycle = 1:number_cycles
    first_index = first_trace_index + (cycle-1) * total_locations ;
    for index = 1:total_locations
        current_index = first_index + (index-1);
        current_index_string = sprintf('%03d', current_index);
        trace_file = [date_string '_' current_index_string '_trace.mat'];
        trace = load(trace_file);
        if empty == 1
            clear data
            data.time = trace.time_values;
            data.values(:,1) = trace.ch0;
            empty = 0;
        else
            data.values(:,(cycle-1)*total_locations+index) = trace.ch0 ;
        end
    end
    if nargin > 4        
        plot(data.time, data.values(:,(cycle-1)*total_locations+1:cycle*total_locations))
        if (cycle == 1)
            hold on
        end
    end
end
if nargin > 4
    grid on
    hold off
end
data.number_cycles = number_cycles;
data.total_locations = total_locations;
data.legend_string = sprintf('%d cycles for locations %s', number_cycles, locations_index_string);
data.locations_x = locations_x;
data.locations_y = locations_y;