percentImprovement(leaders)

function percentImprovement(leaders)

x = [leaders.date];
y = [leaders.percentImprovement];
plot(x,y,'x')

box on
datetick
xlabel('submission time')
ylabel('percent improvement over previous leader  ')
set(gca,'YScale','log')
title('Percent Improvement')

% Find positions of all potential labels.
t = text(x(2),y(2),'foo');
xpos = zeros(size(x));
for i = 1:length(x)
    set(t,'Units','data','position',[x(i) y(i)]);
    set(t,'Units','pixels');
    pos = get(t,'position');
    xpos(i) = pos(1);
end
delete(t)

% Label biggest improvement to smallest, skipping where it's already
% crowded in x-space.
toLabel = false(size(x));
toCheck = false(size(x));
[null,ind] = sort(y,'descend');
textHeight = 15;
for i = 1:length(ind)
    next = ind(i);
    if min([abs(xpos(next)-xpos(toCheck)) Inf]) > textHeight/2
        toLabel(next) = true;

        line(leaders(next).date,leaders(next).percentImprovement,'Marker','x','Color','red')
        text(leaders(next).date,leaders(next).percentImprovement,['  ' leaders(next).author], ...
            'HorizontalAlignment','left','VerticalAlignment','middle', ...
            'Rotation',90)
    end
    toCheck(next) = true;
end