Threshold contour without changing colormap

How can I create a threshold contour without changing an existing colormap? Here is my code:

figure(1)
hold on
m_contourf(lon,lat,(ndustaCNT)',40,'LineStyle','none');
m_contourf(lon,lat,(ndustaCNT)',[0 0],'Color','w');
m_coast('line','Color','k');
m_grid('xtick',10,'tickdir','out','yaxislocation','left','fontsize',10);
c3 = colorbar('WestOutside');

I want to keep the colormap associated with the ndustaCNT matrix but overlay a single white contour where values equal zero. When I add in the second m_contourf line, the colormap changes and I lose all the structure. Thanks for your help. - Sylvia

Answer 1

[Chad Greene]

The freezeColors function on file exchange should solve this problem.

figure(1)
hold on
m_contourf(lon,lat,(ndustaCNT)',40,'LineStyle','none');
freezeColors; 
m_contourf(lon,lat,(ndustaCNT)',[0 0],'Color','w');
m_coast('line','Color','k');
m_grid('xtick',10,'tickdir','out','yaxislocation','left','fontsize',10);
c3 = colorbar('WestOutside');

[Sylvia]

Thanks, I've used freezeColors before and it works very well between subplots, but I've never used it within a single subplot. Actually I just used m_contour rather than m_contourf to make this work:

figure(1)
hold on
m_contourf(lon,lat,(ndustaCNT)',40,'LineStyle','none');
m_contour(lon,lat,(ndustaCNT)',[0 0],'Color','w');
m_coast('line','Color','k');
m_grid('xtick',10,'tickdir','out','yaxislocation','left','fontsize',10);
c3 = colorbar('WestOutside');