# Exercise 12

## Mean of a vector

If we have a vector \(X\) containing \(n\) values, then the mean \(\bar{X}\) is:

\begin{equation} \bar{X} = \frac{1}{n} \sum_{i=1}^{N} \left( X_{i} \right) \end{equation}
In MATLAB, Python (NumPy) and R there are built-in functions for
computing the mean of a vector. Conveniently, in all three languages
the function is called `mean()`

.

In MATLAB:

x = [2,1,5,4,8,3,4,3]; mean(x) ans = 3.7500

In Python / NumPy: (started using `ipython --pylab`

)

x = array([2,1,5,4,8,3,4,3], 'float') mean(x) Out[2]: 3.75

In R:

x <- c(2,1,5,4,8,3,4,3) mean(x) [1] 3.75

## from scratch

Write a function called `mymean()`

that computes the mean of a list of
numbers. Do it from scratch, in other words don't use the built-in
function `mean()`

.