figure explaining diffusion

Author: gertingold

images/diffusion.pdf

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+from pyx import canvas, color, deco, path, text, unit
+
+text.set(text.LatexRunner)
+text.preamble(r'\usepackage{arev}\usepackage[T1]{fontenc}\usepackage{nicefrac}')
+unit.set(xscale=1.0, wscale=1.2)
+
+c = canvas.canvas()
+r = 0.05
+for n in range(1, 5):
+    c.stroke(path.circle(n, 0, r))
+    c.stroke(path.circle(-n, 0, r))
+c.stroke(path.circle(0, 0, r), [deco.filled([color.grey(0)])])
+dx = 0.1
+dy = 0.3
+c.stroke(path.curve(dx, dx, dy, dy, 1-dy, dy, 1-dx, dx), [deco.earrow])
+c.text(0.5, dy+0.1, '+1', [text.halign.center])
+c.stroke(path.curve(-dx, dx, -dy, dy, -1+dy, dy, -1+dx, dx), [deco.earrow])
+c.text(-0.5, dy+0.1, '-1', [text.halign.center])
+c.writePDFfile()