Plotting a multidimensional variable/matrix on a shapefile?

Does anyone know how I can plot a multidimensional variable (rainfall) on a shapefile (country shp) so I can view the spatial distribution of the variable. I tried the code below, but it didn't worked as expected. The image didn't cover the entire area of the shapefile despite all analysis done was to the shape file extent.

Nig=worldmap('Nigeria');
S=shaperead('NGN.shp','UseGeoCoords',true);
set(Nig,'Visible','off')
latlim=getm(Nig,'MapLatlimit');
lonlim=getm(Nig,'MapLonlimit');
geoshow(Nig,S,'FaceColor',[1 1 1]);

%Nigeria meshgrid
NGlon_model = 5:1:13;
NGlat_model = 4:1:15;
NGlat_model = flipud(NGlat_model');

% Create grid
[NGlon,NGlat] = meshgrid(NGlon_model,NGlat_model); 
Rain=RegFP;
geoshow(NGlat,NGlon,(RegFP(:,:,102)),'displaytype','texturemap');

load coastlines
[csrlatcells, csrloncells] = polysplit(coastlat, coastlon);
plotm(coastlat, coastlon,'k')

[KSSV]

Attach your shape file..so that people can help you.