Estou usando o pacote mongolite para conectar e recuperar dados do MongoDB.Como passar valor no mongolite find query

##connecting mongodb

library(mongolite)

mongo<-mongolite::mongo(collection = "Sample", db = "Test", url = 
                          "mongodb://User:123@Wyyuyu:13333/ty2_U",verbose = TRUE)

## getting all data from collection data from collection below query is working fine.

values <- mongo$find()

## But I want to filter specific value by passing value.

 for(i in c("process","check","queue"))
{    

   values <- mongo$find('{"field" : i}',)
}

se eu tentei o código acima, estou ficando abaixo dos problemas. por favor me ajude a resolver

Error: Invalid JSON object: {"field" : i}