How to derive equation from Numpy's polyfit?
<p>Given an array of x and y values, the following code will calculate a regression curve for these data points.</p>

<pre><code># calculate polynomial
z = np.polyfit(x, y, 5)
f = np.poly1d(z)

# calculate new x's and y's
x_new = np.linspace(x[0], x[-1], 50)
y_new = f(x_new)

plt.plot(x,y,'o', x_new, y_new)
plt.xlim([x[0]-1, x[-1] + 1 ])
plt.show()
</code></pre>

<p>How can I use the above to derive the actual equation for this curve?</p>