An sf object of the constituencies submitted to the function. If there are no constituencies, return is NULL.
Arguments
boundary
The resolution of constituencies, e.g. Census Output Areas or Westminster Constituencies. Available boundaries can be found here: https://geoportal.statistics.gov.uk/
col_name_var
The name of the datafield where the constituency name is held, e.g. PCON22NM for 2022 Parliamentary Constituencies.