Superimposing of the boundaries of world countries on a map

Hi I have a matrix (the name of matrix is "matrix_of_cluster") with 55 rows and 144 columns,each guy of this matrix is a number (or NaN) which represents a grid of earth (each grid is 2.5 degree*2.5 degree), this matrix covers latitude: 60S-77.5N and longitude: 180W-180E, I mapped this matrix using the following code. I want to put the boundaries of countries on this map. I tried to use worldmap and geoshow functions, but it did not work. How can I do this? The necessary files have been attached.

Var=matrix_of_cluster;
h1=imagesc(Var);
set(h1,'alphadata',~isnan(Var))
colormap hsv(4)
set(gca,'YDir','normal')
colorbar('location','Eastoutside')

Answer 1

[Chad Greene]

Hi Ehsan,

You can use a function I wrote for this called borders. But your lat,lon values are not correct. You'll need to explicitly state those values when you plot with imagesc.

[Chad Greene]

I tinkered a bit and it looks like you should use lat/lon limits similar to the values below. But you should not use my values--use the actual pixel center locations of your data. Also, the hsv colormap is a bit garish. Are your data categorical or sequential? I used the brewermap function on the file exchange site instead of your hsv(4).

h1=imagesc(linspace(-180,180,144),linspace(-60,75,55),Var);
set(h1,'alphadata',~isnan(Var))
caxis([1 4])
colormap(brewermap(6,'BuGn'))

[Chad Greene]

You can also easily change the background color to ocean blue with rgb.

set(gca,'color',rgb('ocean blue'))

[Sam]

Thanks alot, it worked, my data is categorical, do you know how can I assign a specific color to a number, I have 4 clusters, so it means that the numbers of my matrix are 1,2,3, and 4 (or NaN which are mainly ocean). For example how can I assign red color to number 2 and blue color to number 1. In addition how can I change the thickness of country borders?

[Chad Greene]

You can assign colors in any order you want by specifying their rgb values. For example,

colormap([1 0 0;0 1 0])

creates two-color colormap made up of only red and green. For prettier colormaps I recommend brewermap on file exchange, which could be used with the syntax

colormap(brewermap(4,'Set1'))

to get a nice 4-color colormap. Another option is to use a fancy color picking website like IWantHue and convert from hex values to rgb with hex2rgb if necessary.

% define some random data: 
A = randi(4,10); 

% plot gridded data: 
imagesc(A)

% define a colormap: 
colormap(hex2rgb({'#01A9EF','#B7790B','#67DF91','#82167E'}))

% initialize a colorbar: 
cb = colorbar;

% set color axis limits: 
caxis([0.5 4.5])

% label categorical data: 
set(cb,'ytick',1:4,...
    'yticklabel',{'data 1';'data 2';'data 3';'data 4'})

To change border line width, just use ...,'LineWidth',4) or whatever value thickness you want. Type

showdemo borders_documentation

to see a few examples of that.

[Sam]

Thank you Chad, your answers helped me alot.