# Calculate Shannon entropy

### Description

Calculate Shannon entropy, following Tastle and Wierman.

### Usage

1 | ```
entropy(V)
``` |

### Arguments

`V` |
A frequency vector |

### Details

This function calculates the Shannon entropy following Tastle and Wierman (2007). A frequency vector describes the number of observations in a given category. For example, the vector [10,20,30,15,4] describes 10 observations with position 1, 20 observations with position 2, 30 observations with position 3, 15 observations with position 4, and 4 observations with position 5.

This function follows Tastle and Wierman and ignores categories with zero observations. This does not follow the formula indicated.

See `consensus`

for a function that considers the order of categories.

### Value

The function returns the Shannon entropy.

### Author(s)

Didier Ruedin

### References

Tastle, W., and M. Wierman. 2007. Consensus and dissention: A measure of ordinal dispersion. International Journal of Approximate Reasoning 45 (3): 531-545.

### See Also

`consensus`

### Examples

1 2 3 4 |