Computes a nonlinearity statistic based on Teräsvirta's nonlinearity test of a time series. The statistic is $$10X^2/T$$ where $$X^2$$ is the Chi-squared statistic from Teräsvirta's test, and T is the length of the time series. This takes large values when the series is nonlinear, and values around 0 when the series is linear.

nonlinearity(x)

## Arguments

x a univariate time series

A numeric value.

## Author

Yanfei Kang and Rob J Hyndman

## Examples

nonlinearity(lynx)
#> nonlinearity
#>    0.8959046