filter out short and null holdings

This is @FrederickFa's suggested (quick but not ideal) change to address the problem discussed in #499. This is also discussed in ADO#661, where there seems to be still some debate on the proper long term solution.

3_run_analysis.R

@@ -52,6 +52,8 @@ if (file.exists(equity_input_file)) {
     port_raw_eq <- port_raw_all_eq %>% filter(investor_name == investor_name_select)
 
     port_eq <- calculate_weights(port_raw_eq, "Equity", grouping_variables)
+
+    port_eq <- port_eq %>% filter(port_weight > 0)  # filter out short and null holdings
 
     port_eq <- merge_in_ald(port_eq, ald_scen_eq)
 
@@ -152,6 +154,8 @@ if (file.exists(bonds_inputs_file)) {
     port_raw_cb <- port_raw_all_cb %>% filter(investor_name == investor_name_select)
 
     port_cb <- calculate_weights(port_raw_cb, "Bonds", grouping_variables)
+
+    port_cb <- port_cb %>% filter(port_weight > 0)  # filter our short and null holdings
 
     port_cb <- merge_in_ald(port_cb, ald_scen_cb)