--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/arrowAnnotation.m	Mon Jan 07 16:26:00 2019 +0100
@@ -0,0 +1,23 @@
+% Draw an arrow from p1 to p2, with text attached
+function [h] = arrowAnnotation(p1,p2)
+    ah = gca;
+    xl = ah.XLim(1);
+    xr = ah.XLim(2);
+
+    yl = ah.YLim(1);
+    yr = ah.YLim(2);
+
+    dx = xr - xl;
+    dy = yr - yl;
+
+    s = [
+        ah.Position(1) + (p1(1) - xl)/dx*ah.Position(3),
+        ah.Position(1) + (p2(1) - xl)/dx*ah.Position(3),
+    ];
+    t = [
+        ah.Position(2) + (p1(2) - yl)/dy*ah.Position(4),
+        ah.Position(2) + (p2(2) - yl)/dy*ah.Position(4),
+    ];
+
+    h = annotation('arrow', s, t);
+end