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caculate Cp and Cpk using python numpy
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#!/usr/bin/env python | |
# encoding: utf-8 | |
import numpy as np | |
def Cp(mylist, usl, lsl): | |
arr = np.array(mylist) | |
arr = arr.ravel() | |
sigma = np.std(arr) | |
Cp = float(usl - lsl) / (6*sigma) | |
return Cp | |
def Cpk(mylist, usl, lsl): | |
arr = np.array(mylist) | |
arr = arr.ravel() | |
sigma = np.std(arr) | |
m = np.mean(arr) | |
Cpu = float(usl - m) / (3*sigma) | |
Cpl = float(m - lsl) / (3*sigma) | |
Cpk = np.min([Cpu, Cpl]) | |
return Cpk | |
if __name__ == "__main__": | |
#a1 = np.random.randn(10) | |
#print a1 | |
#print Cp(a1, 1, -1) | |
#print Cpk(a1, 1, -1) | |
a1 = np.arange(0, 10) | |
print a1 | |
print Cp(a1, 10, 0) | |
print Cpk(a1, 10, 0) |
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