lagrange

Author: izaakrogan

lagrange.py

@@ -0,0 +1,18 @@
+# lagragian
+def pi(x,i,xs):
+    xi = xs[i]
+    xs.remove(xi)
+    res = 1;
+    for xj in xs:
+        res *= (x-xj)/(xi-xj)
+    return res
+
+def lagrange(x,xs,ys):
+    res = 0
+    for i in range(len(ys)):
+        res += ys[i]*pi(x,i,xs[:])
+    return res
+
+xs=[1,2,3,4,5,6];
+ys=[0.,0.841471,0.909297,0.14112,-0.756802,-0.958924];
+print(lagrange(1.5,xs,ys))