add linear booster

booster/xgboost.cpp

@@ -12,6 +12,7 @@
 #include "xgboost_gbmbase.h"
 // implementations of boosters
 #include "tree/xgboost_svdf_tree.hpp"
+#include "linear/xgboost_linear.hpp"
 
 namespace xgboost{
     namespace booster{
@@ -21,7 +22,11 @@ namespace xgboost{
          * \return the pointer to the gradient booster created
          */
         IBooster *CreateBooster( int booster_type ){
-            return new RTreeTrainer();
+            switch( booster_type ){
+            case 0: return new RTreeTrainer();
+            case 1: return new LinearBooster();
+            default: utils::Error("unknown booster_type"); return NULL;
+            }
         }
     };
 };