Error using scatterm: LAT and LON, to have NaN-separators in corresponding positions

I'm trying to plot values on a map using the mapping toolbox. The points are given by latitude and longitudes lat1 and lon1, and I would like each point to have a different color, determined by the vector A. I have the following code, but I get an error: "Function SCATTERM expected its first and second input arguments, LAT and LON, to have NaN-separators in corresponding positions."

I'm not sure what this means. How do a create NaN-separators in corresponding positions?

Thanks!

    %create the map axes. See http://www.mathworks.com/help/map/the-map-frame.html
    axesm('MapProjection','robinson',...
         'MapLatLimit',[-90 90],'MapLonLimit',[-180 180], ...
        'Frame','on','Grid','on', 'MeridianLabel', 'off', 'ParallelLabel', 'off')
    %load the coast data and plot. See http://www.mathworks.com/help/map/create-a-world-map.html
    load coast
    [latcells, loncells] = polysplit(lat, long);
    numel(latcells)
    plotm(lat, long,'color',[0 0 0]); hold on
    pointsize=10;
    h1=scatterm(lat1,lon1,pointsize,A);
    colorbar