See this:
http://matlab.cheme.cmu.edu.edu/2011/08/09/phase-portraits-of-a-system-odes/-eodes/
to understand how to make phase portraits in MATLAB. The following shows an example without using for-loop for your equations.
[X1,X2] = meshgrid(-5:0.5:5);
xs = arrayfun(@(x,y) {odeFun([],[x,y])}, X1, X2);
x1s = cellfun(@(x) x(1), xs);
x2s = cellfun(@(x) x(2), xs);
quiver(x1s, x2s)
Xlabel（'x_1')
ylabel（'x_2')
轴tight equal;
功能dxdt = odeFun(t,x)
dxdt（1）= 5*x（1）-9*x（2）;
dxdt(2) = 1*x(1)-5*x(2);
end
