This function shifts the reference frame of an isotopic data object
that has a reference associated (currently only `delta`

values.

shift_reference(iso, ref) # S4 method for ANY,ANY shift_reference(iso, ref) # S4 method for Delta,Delta shift_reference(iso, ref)

iso | the isotope object whose reference frame to shift (delta) |
---|---|

ref | the isotope object which is relative to the new reference frame (delta) |

a delta value with the shifted reference

The function requires the reference of the first delta value to
the compound measured in the second delta value. This calculations is
also implemented with an `arithmetic`

shorthand. All calculatinos are
only permissible if the fractionation factors and isotope values have matching
attributes.

Other operations: `fractionate`

,
`mass_balance`