Map/ Figure with white color bar assignment to the lowest value

Sometimes we need the figures or plots showing the maps. The oceans/missing values are indicated in the data as NaN or -9999. This code will plot the data with the lowest value being shown as white color.

A = rand(55);

figure;
imagesc(A)
colormap(jet(33))
map2 = colormap; map2( 1, : ) = 1; colormap(map2)
cmap = colormap; % cmap nicely puts colormap into 3 col data
colorbar