angular js - condition in select "comprehension expression"

im not super fluent with js so some of my terminology might be off, buttttt

i've got an angular app that maps one set of objects to another set of objects via two select elements.
when a mapping is made, the mapped objects' "mapped" property gets set to true.

<select ng-model='sourceToMap' required='true' ng-options='code.code for code in sourceCodes'>
<select ng-model='targetToMap' required='true' ng-options='code.code for code in targetCodes'></select>

i'd like my select to show all the items in sourceCodes/targetCodes whose mapped property is false. something like...

ng-options="code.code for code in sourceCodes where code.mapped = false"

if possible, i'd like to avoid having a mappedItems / unmappedItems collection cause that seems really gross