New ScreenPanel

script/fit_radius.py

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+from mathutils import *
+
+#Fiting center of circle of radius 70  to observerd points
+radius = 70.0
+x = [30.0,  50.0, 110.0, 35.0, 45.0]
+y = [68.0,  -6.0, -20.0, 15.0, 97.0]
+p = plot(y, xdata=x)[0]
+num_samples = len(x)
+w = [ 1.0] * num_samples
+w = [0.1,  0.1, 1.0, 0.1, 1.0]
+#I = MatrixUtils.createRealIdentityMatrix(len(w))
+W = MatrixUtils.createRealDiagonalMatrix(w)
+
+
+  # the model function components are the distances to current estimated center,
+  # they should be as close as possible to the specified radius
+class Model(MultivariateJacobianFunction):
+    def value(self, variables):
+        (cx,cy) = (variables.getEntry(0), variables.getEntry(1))  
+        value = ArrayRealVector(num_samples)
+        jacobian = Array2DRowRealMatrix(num_samples, 2)
+        for i in range(num_samples):
+            model = math.hypot(cx-x[i], cy-y[i]) 
+            value.setEntry(i, model)
+            # derivative with respect to p0 = x center
+            jacobian.setEntry(i, 0, (cx - x[i]) / model)
+            # derivative with respect to p1 = y center
+            jacobian.setEntry(i, 1, (cy - y[i]) / model)
+        return Pair(value, jacobian)
+
+model = Model()
+
+# the target is to have all points at the specified radius from the center
+target = [radius,] * num_samples
+
+#least squares problem to solve : modeled radius should be close to target radius
+initial = [0.0, 0.0 ]
+problem = LeastSquaresBuilder().start(initial).model(model).target(target).lazyEvaluation(False).maxEvaluations(1000).maxIterations(1000).weight(W).build()
+optimizer = LevenbergMarquardtOptimizer()
+optimum = optimizer.optimize(problem)
+cx, cy = optimum.getPoint().getEntry(0), optimum.getPoint().getEntry(1)
+
+print "fitted center x: ", cx
+print "fitted center y: ", cy
+print ""
+print "RMS: "          , optimum.getRMS()
+print "evaluations: "  , optimum.getEvaluations()
+print "iterations: "   , optimum.getIterations()
+
+from plotutils import *
+
+plot_point(p, cx, cy, name="Fit Cente")
+plot_circle(p, cx, cy, radius, name="Fit")
+