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script/CPython/extremum.py

@@ -1,13 +1,10 @@
 import numpy as np
 
-
 def extremum(x, y):
     """
     Return extremum coordinates of quadratic fit
     """
-    pf = np.polyfit(x, y, 2, full=True)
-    p = pf[0]
-    res = pf[1][0]
+    p = np.polyfit(x, y, 2)
     f = np.poly1d(p)
     if p[0] != 0:
         x_ext = -p[1] / (2 * p[0])
@@ -15,6 +12,11 @@ def extremum(x, y):
     else:
         x_ext = None
         y_ext = None
+    yhat = f(x)
+    ybar = np.sum(y)/len(y)
+    ssreg = np.sum((yhat - ybar)**2)
+    sstot = np.sum((y - ybar)**2)
+    R2 = ssreg / sstot
     x_fit = np.linspace(min(x), max(x), 100)
     y_fit = f(x_fit)
-    return (x_ext, y_ext, x_fit, y_fit, res)
+    return (x_ext, y_ext, x_fit, y_fit, R2)