| generate_data | generate response from nonparametric additive model |
| kko | variable selection for additive model via KKO |
| KO_evaluation | evaluate performance of KKO selection |
| rk_fit | nonparametric additive model seleciton via random kernel |
| rk_subsample | compute selection frequency of rk_fit on subsamples |
| rk_tune | tune random feature number for KKO. |