added script

scripts/gradients.m

+clear all
+clf
+
+tx = ty = linspace (-2, 2, 41)';
+[xx, yy] = meshgrid (tx, ty);
+tz = xx.^2 + yy.^2;
+
+mesh(tx, ty, tz)
+
+hold on
+
+[x, y] = meshgrid (-2:0.2:2);
+h = quiver (x, y, 2*x, 2*y);
+set (h, "maxheadsize", 0.33);
+
+hold off