# xarray.concat

`xarray.``concat`(objs, dim, data_vars='all', coords='different', compat='equals', positions=None, fill_value=<NA>, join='outer')

  Concatenate xarray objects along a new or existing dimension.

  Parameters:

  - objs (sequence of Dataset and DataArray objects) – xarray objects to concatenate together. Each object is expected to consist of variables and coordinates with matching shapes except for along the concatenated dimension.
  - dim (str or DataArray or pandas.Index) – Name of the dimension to concatenate along. This can either be a new dimension name, in which case it is added along axis=0, or an existing dimension name, in which case the location of the dimension is unchanged. If dimension is provided as a DataArray or Index, its name is used as the dimension to concatenate along and the values are added as a coordinate.
  - data_vars ({'minimal', 'different', 'all' or list of str}, optional) –
    These data variables will be concatenated together:
      - ’minimal’: Only data variables in which the dimension already appears are included.
      - ’different’: Data variables which are not equal (ignoring attributes) across all datasets are also concatenated (as well as all for which dimension already appears). Beware: this option may load the data payload of data variables into memory if they are not already loaded.
      - ’all’: All data variables will be concatenated.
      - list of str: The listed data variables will be concatenated, in addition to the ‘minimal’ data variables.

    If objects are DataArrays, data_vars must be ‘all’.

  - coords ({'minimal', 'different', 'all' or list of str}, optional) –
    These coordinate variables will be concatenated together:
      - ’minimal’: Only coordinates in which the dimension already appears are included.
      - ’different’: Coordinates which are not equal (ignoring attributes) across all datasets are also concatenated (as well as all for which dimension already appears). Beware: this option may load the data payload of coordinate variables into memory if they are not already loaded.
      - ’all’: All coordinate variables will be concatenated, except those corresponding to other dimensions.
      - list of str: The listed coordinate variables will be concatenated, in addition to the ‘minimal’ coordinates.
  - compat ({'identical', 'equals', 'broadcast_equals', 'no_conflicts', 'override'}, optional) –

    String indicating how to compare non-concatenated variables of the same name for potential conflicts. This is passed down to merge.

    - ’broadcast_equals’: all values must be equal when variables are broadcast against each other to ensure common dimensions.
    - ’equals’: all values and dimensions must be the same.
    - ’identical’: all values, dimensions and attributes must be the same.
    - ’no_conflicts’: only values which are not null in both datasets must be equal. The returned dataset then contains the combination of all non-null values.
    - ’override’: skip comparing and pick variable from first dataset
  - positions (None or list of integer arrays, optional) – List of integer arrays which specifies the integer positions to which to assign each dataset along the concatenated dimension. If not supplied, objects are concatenated in the provided order.
  - fill_value (scalar, optional) – Value to use for newly missing values
  - join ({'outer', 'inner', 'left', 'right', 'exact'}, optional) –

    String indicating how to combine differing indexes (excluding dim) in objects

    - ’outer’: use the union of object indexes
    - ’inner’: use the intersection of object indexes
    - ’left’: use indexes from the first object with each dimension
    - ’right’: use indexes from the last object with each dimension
    - ’exact’: instead of aligning, raise ValueError when indexes to be aligned are not equal
    - ’override’: if indexes are of same size, rewrite indexes to be those of the first object with that dimension. Indexes for the same dimension must have the same size in all objects.

  Returns: | concatenated
  Return type: | type of objs

  Notes

  Each concatenated Variable preserves corresponding `attrs` from the first element of `objs`.

  See also

  `merge()`, `auto_combine()`