# cf.Field.insert_axis

`Field.``insert_axis`(axis, key=None, replace=True)

  Insert a domain axis into the field.

  See also

  `insert_aux`, `insert_measure`, `insert_ref`, `insert_data`, `insert_dim`

  Parameters: | axis: `cf.DomainAxis` The new domain axis. key: `str`, optional The identifier for the new axis. By default a new, unique identifier is generated. replace: `bool`, optional If False then do not replace an existing axis with the same identifier but a different size. By default an existing axis with the same identifier is changed to have the new size.
  Returns: | out: `str` The identifier of the new domain axis.
  Examples: |

      >>> f.insert_axis(cf.DomainAxis(1))
      >>> f.insert_axis(cf.DomainAxis(90), key='dim4')
      >>> f.insert_axis(cf.DomainAxis(23), key='dim0', replace=False)