xarray.Dataset.traj.iseltime#

abstract Dataset.traj.iseltime(i)#

Select observations by index (of non-nan, time, observation) across trajectories. For 1D datasets prefer to use xarray.Dataset.isel.

Parameters:: i (index, list of indexes or a slice.)
Returns:: ds (Dataset) – A dataset with the selected indexes in each trajectory.

Example

Select the first and last element in each trajectory in a dataset of unstructured observations:

>>> import xarray as xr
>>> import trajan as _
>>> import lzma
>>> b = lzma.open('examples/barents.nc.xz')
>>> ds = xr.open_dataset(b)
>>> print(ds)
<xarray.Dataset> Size: 110kB
Dimensions:        (trajectory: 2, obs: 2287)
Dimensions without coordinates: trajectory, obs
Data variables:
    lon            (trajectory, obs) float64 37kB ...
    lat            (trajectory, obs) float64 37kB ...
    time           (trajectory, obs) datetime64[ns] 37kB ...
    drifter_names  (trajectory) <U16 128B ...
Attributes: (12/13)
    Conventions:          CF-1.10
    featureType:          trajectory
    geospatial_lat_min:   74.5454462
    geospatial_lat_max:   77.4774768
    geospatial_lon_min:   17.2058074
    geospatial_lon_max:   29.8523485
    ...                   ...
    time_coverage_end:    2022-11-23T13:30:28
    creator_email:        gauteh@met.no, knutfd@met.no
    creator_name:         Gaute Hope and Knut Frode Dagestad
    creator_url:          https://github.com/OpenDrift/opendrift
    summary:              Two drifters in the Barents Sea. One stranded at Ho...
    title:                Barents Sea drifters

>>> ds = ds.traj.iseltime([0, -1])
>>> print(ds)
<xarray.Dataset> Size: 224B
Dimensions:        (trajectory: 2, obs: 2)
Dimensions without coordinates: trajectory, obs
Data variables:
    lon            (trajectory, obs) float64 32B 29.85 25.11 27.82 21.15
    lat            (trajectory, obs) float64 32B 77.3 76.57 77.11 74.58
    time           (trajectory, obs) datetime64[ns] 32B 2022-10-07T00:00:38 ....
    drifter_names  (trajectory) <U16 128B 'UIB-2022-TILL-01' 'UIB-2022-TILL-02'
Attributes: (12/13)
    Conventions:          CF-1.10
    featureType:          trajectory
    geospatial_lat_min:   74.5454462
    geospatial_lat_max:   77.4774768
    geospatial_lon_min:   17.2058074
    geospatial_lon_max:   29.8523485
    ...                   ...
    time_coverage_end:    2022-11-23T13:30:28
    creator_email:        gauteh@met.no, knutfd@met.no
    creator_name:         Gaute Hope and Knut Frode Dagestad
    creator_url:          https://github.com/OpenDrift/opendrift
    summary:              Two drifters in the Barents Sea. One stranded at Ho...
    title:                Barents Sea drifters