Computes feature of a time series based on tiled (non-overlapping) windows.
Means or variances are produced for all tiled windows. Then stability is
the variance of the means, while lumpiness is the variance of the variances.

## Arguments

- x
a univariate time series

- width
size of sliding window

## Value

A numeric vector of length 2 containing a measure of lumpiness and
a measure of stability.

## Author

Earo Wang and Rob J Hyndman