How to get arrows on axes in MATLAB plot?

Question

I want to plot something like this:

x = 0:0.01:10;
f = @(x) 50* 1.6.^(-x-5);
g = @(x) 50* 1.6.^(+x-10);
plot(x, f(x));
hold on
plot(x, g(x));

I

Answer 1

Well, don't say I didn't warn you :)

% Some bogus functions
f = @(x) 50* 1.6.^(-x-5);
g = @(x) 50* 1.6.^(+x-10);

% Point where they meet
xE = 2.5;
yE = f(xE);

% Plot the bogus functions
figure(1), clf, hold on
x = 0:0.2:5;
plot(x,f(x),'r',  x,g(x),'b', 'linewidth', 2)

% get rid of standard axes decorations
set(gca, 'Xtick', [], 'Ytick', [], 'box', 'off')

% Fix the axes sizes
axis([0 5 0 5])

% the equilibrium point
plot(xE, yE, 'k.', 'markersize', 20)

% the dashed lines
line([xE 0; xE xE], [0 yE; yE yE], 'linestyle', '--', 'color', 'k')

% the arrows
xO = 0.2;  
yO = 0.1;
patch(...
    [5-xO -yO; 5-xO +yO; 5.0 0.0], ...
    [yO 5-xO; -yO 5-xO; 0 5], 'k', 'clipping', 'off')

% the squishy wiggly line pointing to the "equilibrium" text
h = @(x)0.5*(x+0.2) + 0.1*sin((x+0.2)*14);
x = 2.7:0.01:3.5;
plot(x, h(x), 'k', 'linewidth', 2)

% the static texts
text(xE-yO, -0.2, 'Q^*', 'fontweight', 'bold')
text(-2*yO,   yE, 'P^*', 'fontweight', 'bold')
text(-2*yO,    4, 'Price', 'rotation', 90, 'fontsize', 14)
text(    4, -0.2, 'Quantity', 'fontsize', 14)
text(   .5,  4.2, 'Demand', 'fontsize', 14, 'rotation', -55)
text(   4.0,  3.3, 'Supply', 'fontsize', 14, 'rotation', +55)
text(   3.6,  2.1, 'Equilibrium', 'fontsize', 14)

Result: