Thanks Bob. I am using your snippet within the getResources call to give me the list of resources to output and it works very well - thanks!
Last pain on this code is that within the infinite scroll getPage code I have for the rest of the results of resources - having an issue where using sortBy Rand messes things up and it lists the same results as per support note here > https://community.modx.com/t/getpage-infinite-scroll-duplicate-results-problem/1922/4
Any ideas on that one?