visuals

FSA04/kcenter.py

+import sys
+import numpy as np
+import matplotlib.pyplot as plt
+
+# load the points
+data = np.loadtxt(sys.stdin,skiprows=1)
+
+# set the aspect ratio to equal
+plt.gca().set_aspect('equal')
+
+# plot the centers (if additional command line arguments present)
+if (len(sys.argv)-2 > 0):
+    ctr = np.array([int(s) for s in sys.argv[2:]])
+    dist_sq = np.zeros((len(ctr),len(data)))
+    for i in range(len(ctr)):
+        dist_sq[i] = np.sum((data-data[ctr[i]])*(data-data[ctr[i]]),axis=1)
+    clu = np.argmin(dist_sq,axis=0)
+    ex = np.argmax(np.min(dist_sq,axis=0))
+    cost_sq = np.max(np.min(dist_sq,axis=0))
+    plt.scatter (data[:,0],data[:,1],c=clu,cmap="tab10",s=10,alpha=0.5)
+    plt.scatter (data[ctr,0],data[ctr,1],c=range(len(ctr)),cmap="tab10",s=100)
+    plt.scatter (data[ex,0],data[ex,1],s=50,facecolors='none', edgecolors='black')
+    plt.title ('Cost = %g' % np.sqrt(cost_sq))
+else:
+    plt.scatter (data[:,0],data[:,1],s=10,color='black')
+
+#save the plot as an image
+plt.savefig(sys.argv[1])