Why the contourfm not perform the contours correctly?

Dear All,

I would like to create some maps by contourfm function, but I found that it does not work correctly. I have some matrices wich have different values between 1 and 31. When I create a map by:

worldmap('Europe');
load coast;
plotm(lat, long, 'k');
clear lat long;
contourfm(latitude,longitude,IU2,30);
caxis([1 31])
contourcmap('coeppen', 'Colorbar', 'on', 'Location', 'horizontal')

I get an incorrect map because there are some contours between same colours. But when I change the contour values from 30 to 29 the contours divide the different values correctly but the colourbar size is just 30 instead of 31 hence the applied colours are incorrect. How should I set up the contourfm and contourcmap functions for perform a correct map?