Using Cython with NumPy

We can integrate Cython and NumPy code in the same way that we can integrate Cython and Python code. Let's go through an example that analyzes the ratio of up days (days on which a stock closes higher than the previous day) for a stock. We will apply the formula for binomial proportion confidence. You can refer to http://en.wikipedia.org/wiki/Binomial_proportion_confidence_interval for more information. This indicates how significant the ratio is.

How to do it...

This section describes how we can use Cython with NumPy. To demonstrate this, perform the following steps:

1. Write the .pyx file.

   Let's write a .pyx file that contains a function to calculate the ratio of up days and associated confidence. First, this function computes the differences of the prices. Then, we count the number of positive differences, giving us a ratio for the proportion of up days. Finally, we apply the formula for the confidence from the Wikipedia page in the introduction.

   import numpy
   
   def pos_confidence...