This function is somewhat analogous to `subset.data.frame()`

, but
subsetting is only permitted by time.

```
# S4 method for sealevel
subset(x, subset, ...)
```

- x
a sealevel object.

- subset
a condition to be applied to the

`data`

portion of`x`

.- ...
ignored.

A new `sealevel`

object.

Other things related to sealevel data:
`[[,sealevel-method`

,
`[[<-,sealevel-method`

,
`as.sealevel()`

,
`plot,sealevel-method`

,
`read.sealevel()`

,
`sealevel`

,
`sealevel-class`

,
`sealevelTuktoyaktuk`

,
`summary,sealevel-method`

Other functions that subset oce objects:
`subset,adp-method`

,
`subset,adv-method`

,
`subset,amsr-method`

,
`subset,argo-method`

,
`subset,cm-method`

,
`subset,coastline-method`

,
`subset,ctd-method`

,
`subset,echosounder-method`

,
`subset,lobo-method`

,
`subset,met-method`

,
`subset,oce-method`

,
`subset,odf-method`

,
`subset,rsk-method`

,
`subset,section-method`

,
`subset,topo-method`

,
`subset,xbt-method`