Remove redundant methods

include/PenningTrap.hpp

@@ -91,10 +91,6 @@ public:
     void evolve_forward_euler(double dt);
 
     sim_arr simulate(double time, int steps, std::string method = "rk4");
-
-    arma::vec get_particle(int i);
-
-    double get_d();
 };
 
 #endif

src/PenningTrap.cpp

@@ -242,12 +242,4 @@ sim_arr PenningTrap::simulate(double time, int steps, std::string method)
     return res;
 }
 
-arma::vec PenningTrap::get_particle(int i)
-{
-    return this->particles.at(i).r_vec;
-}
 
-double PenningTrap::get_d()
-{
-    return this->d;
-}