# Chapter 12

## MATLAB Code Examples

```function mean = stats(x)
if ~isvector(x)
error(‘Input must be a vector’)
end
mean = sum(x)/length(x);
end```
```function [mean, sdev] = stats(x)
if ~isvector(x)
error(‘Input must be a vector’)
end
len = length(x);
mean = sum(x)/len;
sdev = sqrt(sum((x-mean).^2/len));
end```

## Python Code Examples

```import numpy as np

# Function definition is here
def stats( my_array ):
"This calculates the mean of the input array"
mean = np.sum(my_array)/np.size(my_array)
return mean

# Now you can call stats function
m = stats([4,5,6])
print(m)```

## Exercises

1. Write a function that calculates the factorial for the input value..
2. Write a function that calculates the factorial for each value of an input vector, and returns a vector of results.
3. Write a function that takes an input matrix, and calculates the average value of each row (or – if instructed by an optional argument – the average value of each column) and returns a vector containing the results
4. Package your functions from these exercises into a custom Python module.