In the function definition you have mentioned 'krad' for the radius of a circle search with 'pcode' as the centre but you can also define the centre directly using 'lat and 'lng'
There is also a 'bounds' parameter where you can supply a boundary polygon but not sure if that is of use
As documented here https://github.com/cyipt/acton/issues/69#issuecomment-754146428