By default, uses linear interpolation for non-seasonal series. For seasonal series, a
robust STL decomposition is first computed. Then a linear interpolation is applied to the
seasonally adjusted data, and the seasonal component is added back.

## Arguments

- x
time series

- lambda
Box-Cox transformation parameter. If `lambda="auto"`

,
then a transformation is automatically selected using `BoxCox.lambda`

.
The transformation is ignored if NULL. Otherwise,
data transformed before model is estimated.

- linear
Should a linear interpolation be used.

## Details

A more general and flexible approach is available using `na.approx`

in
the `zoo`

package.