Quantify the smoothness of a vector

`smoothness(x, method = "cor", lag = 1, iterations = NULL, ...)`

## Arguments

x |
Numeric vector (similar to a time series). |

method |
Can be "diff" (the standard deviation of the standardized
differences) or "cor" (default, lag-one autocorrelation). |

lag |
An integer indicating which lag to use. If less than 1, will be
interpreted as expressed in percentage of the length of the vector. |

iterations |
The number of bootstrap replicates for computing standard
errors. If `NULL` (default), parametric standard errors are computed. |

... |
Arguments passed to or from other methods. |

## Value

Value of smoothness.

## References

https://stats.stackexchange.com/questions/24607/how-to-measure-smoothness-of-a-time-series-in-r

## Examples

```
x <- (-10:10)^3 + rnorm(21, 0, 100)
plot(x)
smoothness(x, method = "cor")
#> [1] 0.9483709
#> attr(,"class")
#> [1] "parameters_smoothness" "numeric"
smoothness(x, method = "diff")
#> [1] 1.395158
#> attr(,"class")
#> [1] "parameters_smoothness" "numeric"
```